Over cellular modems in the drones with Russian SIM cards. The operation was prepared for months in advance. Getting a bunch of pre-paid SIM cards from the Russian equivalent to 7-11 (which might just be 7-11) was probably the easiest part of the operation.
Stores won't sell a SIM card without the buyer providing valid state ID, and SIM cards are disabled by carriers if they suspect you are using someone else's card and you can't provide an ID for it. This is one of the recent laws. Getting a phone number/data plan that isn't associated with your real identity (and instead registered to someone else, usually a homeless guy somewhere) isn't impossible, but those wouldn't come from a grocery store.
They've been planning this for over a year and this is the SBU we're talking about. I'm pretty sure they could figure out a way to light up a data plan on a cell phone in Russia when needed.
Or just their civilian phones. Suddenly occurs to me how effective that would be as a source of SIMs. Won't last forever but can be produced in the month preceding the op.
Maybe just tourist SIMs that let you roam into other countries? Buy a load of SIMs in Kazakhstan or somewhere like that, roam into Russia, now you have internet?
Jamming only works when there's equipment in place and activated. Prior to this attack there was no reason for Russia to even have jamming equipment located at a base deep inside their borders let alone active.
