I think in every country you could give 5$ to a bum asking to buy a phone. In Russia burner phones is also kinda illegal. But in idiotic form. There is a lag about a week long between moment you starting using a phone and the moment when MNO is deactivating your number because it was not linked with ID (passport No). So you could buy a sim-card, but you should activate it in a week. So the funny moment have place, this week is enough for any kind of criminal activity, but if you are planning to use number for a long time it should be personalised. Also there is a huge black market of sim cards, the sweetest ones is without time limit and leaking from the business/enterprise MNO plans, it's supposed that the company is responsible for how numbers related to the corporate plan is used.

As far as i understand phones was burned after some time frame, not even after single call. But i think tracking events like "First call from a new IMSI" with geo-linking could reveal some patterns that breaking even single-call-then-trash schema. If you could track facts of selling prepaid phones - there is even more data whatever is it many phones was bought at once or on-demand purchases has place.