I'm reading Young Stalin and in chapter 12 Montefiore talks about when Stalin was sent to exile in Novoya Uda.
"He cut his Jewish fellow exiles but embraced the local hobby: pubcrawls with the criminals" to the point that the other 'middle-class snobbish' revolutionary exiles, organized a 'comrade's court' to put Stalin on trial for drinking with criminals.
But how the hell do you even, as an exile from Georgia, find these criminals, and then socialize successfully with them to go on pubcrawls? Right now I can see two pathways, 1. through his accommodation (he shared the same room as a peasant family, who could be in a social-network with criminals), 2. through taverns (which still, how? Did Stalin just walk up to a circle of locals and introduce himself and coincidentally they were criminals?).
Many exiles in Siberia were given a large degree of freedom, in that they weren't confined to a prison or anything like that, and simply had to check in with authorities at set times. The rationale behind this is the simple fact that Siberia is vast, it's mostly empty, and it's incredibly difficult to traverse (in summer it's mostly unpassable marshland, in winter it's incredibly cold). So if a convict escaped, they faced a several thousand kilometre trek back to their homes, and with really only one or two routes in and out of Siberia, it was rather easy for the authorities to find and recapture them (stretched as they were; the Russian imperial government chronically underfunded and understaffed their Siberian penal administration). That said, convicts did still escape, and did so frequently. I can't recall where Montefiore mentions it in his book, and I apologize for potentially spoiling this, but Stalin himself does escape Siberia (only to be re-captured; he did this a few times before a final exile).
As for how convicts would find each other, it's quite simple: they lived in the same communities, and if they were out in more remote regions (as Stalin was during his Turukhansk exile), they would meet up in larger trading centres. During these visits they would exchange books, notes, discuss life and so on, anything to pass the boredom of the time. Some convicts were sentenced to hard labour, so would be involved in something like that, but I don't believe Stalin had anything like that.
Convicts would be well-aware of each other as well, at least amongst the Bolsheviks, as they kept a close and effective network. Even with contacts literally spread across the breath of Eurasia (from France to Siberia), they were able to keep accurate tabs on each other, relatively speaking (though not close enough to notice several secret police infiltrators). This meant that when Stalin, or whomever, went into exile, he would know who else was around him, and how to reach them.
If you'd like to read more on the Siberian exile system as a whole, I'd strongly recommend The House of the Dead: Siberian Exile Under the Tsars by Daniel Beer (2017). It's a well-cited book, but not overtly academic and really engaging, and while the focus is on the nineteenth century (so just before the Bolsheviks really started to get exiled), it still gives a solid idea of what they were getting into.
For Stalin specifically, you're already reading Young Stalin by Simon Sebag Montefiore (2007), but there's also two books I'd recommend:
I would also really recommend Stalin: Passage to Revolution by Ronald Grigor Suny (2020). Suny has been working on this book for 30 years, and it's not a conventional biography, but a look at the background of Stalin and why he ended up where he did. It has a very in depth look at his Siberian exile and how that impacted his life.