On the thirteenth of June a rather small, thoroughbred Arab horse was brought to Napoleon. He mounted it and rode at a gallop to one of the bridges over the Niemen, deafened continually by incessant and rapturous acclamations which he evidently endured only because it was impossible to forbid the soldiers to express their love of him by such shouting, but the shouting which accompanied him everywhere disturbed him and distracted him from the military cares that had occupied him from the time he joined the army. He rode across one of the swaying pontoon bridges to the farther side, turned sharply to the left, and galloped in the direction of Kóvno, preceded by enraptured, mounted chasseurs of the Guard who, breathless with delight, galloped ahead to clear a path for him through the troops. On reaching the broad river Víliya, he stopped near a regiment of Polish Uhlans stationed by the river.
"Vivat!" shouted the Poles, ecstatically, breaking their ranks and pressing against one another to see him.
Napoleon looked up and down the river, dismounted, and sat down on a log that lay on the bank. At a mute sign from him, a telescope was handed him which he rested on the back of a happy page who had run up to him, and he gazed at the opposite bank. Then he became absorbed in a map laid out on the logs. Without lifting his head he said something, and two of his aides-de-camp galloped off to the Polish Uhlans.
"What? What did he say?" was heard in the ranks of the Polish Uhlans when one of the aides-de-camp rode up to them.
The order was to find a ford and to cross the river. The colonel of the Polish Uhlans, a handsome old man, flushed and, fumbling in his speech from excitement, asked the aide-de-camp whether he would be permitted to swim the river with his Uhlans instead of seeking a ford. In evident fear of refusal, like a boy asking for permission to get on a horse, he begged to be allowed to swim across the river before the Emperor’s eyes. The aide-de-camp replied that probably the Emperor would not be displeased at this excess of zeal.
As soon as the aide-de-camp had said this, the old mustached officer, with happy face and sparkling eyes, raised his saber, shouted "Vivat!" and, commanding the Uhlans to follow him, spurred his horse and galloped into the river. He gave an angry thrust to his horse, which had grown restive under him, and plunged into the water, heading for the deepest part where the current was swift. Hundreds of Uhlans galloped in after him. It was cold and uncanny in the rapid current in the middle of the stream, and the Uhlans caught hold of one another as they fell off their horses. Some of the horses were drowned and some of the men; the others tried to swim on, some in the saddle and some clinging to their horses’ manes. They tried to make their way forward to the opposite bank and, though there was a ford one third of a mile away, were proud that they were swimming and drowning in this river under the eyes of the man who sat on the log and was not even looking at what they were doing. When the aide-de-camp, having returned and choosing an opportune moment, ventured to draw the Emperor’s attention to the devotion of the Poles to his person, the little man in the gray overcoat got up and, having summoned Berthier, began pacing up and down the bank with him, giving him instructions and occasionally glancing disapprovingly at the drowning Uhlans who distracted his attention.
For him it was no new conviction that his presence in any part of the world, from Africa to the steppes of Muscovy alike, was enough to dumfound people and impel them to insane self-oblivion. He called for his horse and rode to his quarters.
Some forty Uhlans were drowned in the river, though boats were sent to their assistance. The majority struggled back to the bank from which they had started. The colonel and some of his men got across and with difficulty clambered out on the further bank. And as soon as they had got out, in their soaked and streaming clothes, they shouted “Vivat!” and looked ecstatically at the spot where Napoleon had been but where he no longer was and at that moment considered themselves happy.
In a nutshell: No but theres a caveat
I would certainly take ANY sort of detail from W&P with a grain of salt if you're looking for exact historical accuracy. Tolstoy's writing is certainly accurate in a broad sense*(Historical figures, battles, events), but he does tend to add in some historically unsupported details to spice up the reading(And it works, it certainly does breathe life into events of the Napoelonic wars)* .
There are a few examples I could bring up but one obvious section would have to be the part near the beginning involving Murat and the Bridge of Tabor. It is certainly true that Murat and Lannes did indeed pull off an amazing bluff against the Austrians. BUT the numerous "flowery" details like Murat dressing down an Austrian officer for letting his[The Austrians] lowly "rankers" speaking in an offensive manner or Murat laying his leg on one of the Austrian cannons(IIRC), are things I haven't really found elsewhere in any reliable sources of the period, they appear to simply be additions made by Tolstoy to make the "story" seem more exciting.
As a result I'd have to chalk it up to flamboyant details for the sake of fun reading. In regards to your excerpt about the Polish Uhlans and their fanatical adoration for Emperor Bonaparte, I would definetly say that an event like that*(As is described by Tolstoy)* Did not happen, but perhaps something similar but less exciting may have