Initially, meaning in the hours and days after Phnom Penh was “liberated” by the Khmer Rouge, there was a rather chaotic period of looting. People deported from the city remembered seeing convoys of trucks and requisitioned cars, loaded with bicycles, furniture, electrical appliances, motor bikes, pharmaceutical goods and radio sets heading in the direction of the Eastern Zone, as well as the South-West and North. Philip Short in his biography of Pol Pot claims that these goods were being treated almost like ‘booty’ for the warlords that oversaw those particular zones. This coincided with a period where the central party leadership had not assumed complete control of governance.

Following this, the Khmer Rouge had units of removal teams move through many houses within the city, their instructions were to ‘leave the revolutionary minimum’, which was a bed without a mattress, a chair without a cushion, and a table. They were told to remove anything worth keeping for use at a later time, which was sent to large warehouses, and to burn the rest. This was coupled with some operations to clear out areas of the city that had been previously occupied by the many thousands of refugees from the country side that had sought refuge in the capital prior to the end of the civil war.

Likewise, in the central districts, the pavements were swept of the kind of detritus that had accumulated in the last months of the Lon Nol regime.

The leadership also began ‘moving in’, occupying buildings and blocks for specific purposes.

However many parts of the city were left untended. Short eloquently describes this in the same source I mentioned above:

The city’s parks and gardens were given over to ‘useful’ trees and plants: frangipane, for traditional medicine, guavas, bananas; and, along the pavements, coconut palms … If Phnom Penh itself could not be physically uprooted and transferred to the countryside, as its population had been, nature would be allowed, wherever possible, to reassert its rights, eliding the difference between worker and peasant, mental and manual labour, and exerting a pristine, regenerative influence on the new revolutionary elite.

There were still around 50,000 people who remained in Phnom Penh or were sent there after the liberation in April '75.

Andrew Mertha, in his book "Brothers in Arms: Chinese Aid to the Khmer Rouge", states that there was a section of the city where the foreign embassies were set up, as well as the shops that these diplomats were able to visit. Various factories, warehouses, hospitals, motor pools and logistics stations were scattered around the city, but movement was strictly controlled and enforced. Particularly sensitive areas, such as the S-21 prison complex, were surrounded by a kind of ‘buffer zone’ so that the activities taking place there would not be noticed by outsiders.

So it was certainly not empty, and the various ministries that were set up would usually mean that top officials and their families may also be relocated to the capital. The airport remained functional and the city, to some degree, was morphed into something resembling a hub for the regime. Zone leaders and cadre could be summoned there, likewise foreign dignitaries who visited.

The Vietnamese who entered the city in January of ’79 did find that it had been largely abandoned again, by any Khmer Rouge in particular, but those who had not joined in that exodus would have remained.