Well; Let's say that in the first instance those who live on the border, where literally the cities are separated by a few meters, there is cellular connections available, of both countries, in this case one of them would be blocked.I have been in border places where the Internet connection is better in Mbps that the neighboring and literal country sell these connections with the use of antennas that you can get on ebay and then an antenna point to point of the other side of the border works.
Then you've never been to a Russian border.

This shutdown will probably most likely include Belarus, this is how Belarus borders to western countries looks like:

with the Baltic states, the border is mainly a lake and a river and there are almost no Russian villages there the rest will be with Ukraine, lol, and Kazakhstan, Mongolia, and China mainly, champions of freedom and countries known to let poeple host free internet connections.
All the borders have been exactly cut like this strategically, remember it's the Russia we're talking about, this is not a border between Belgium and Netherlands.

Also, if you want to censor those things it's pretty easy, wi-fi jammers are far more effective than the wifi themselves and it will take simple things to block them, not even counting what Russia
has on its border for every kind of radio signal already.
How many North Koreans you have seen around this forum?
If you were a North Korean who had gained access to the rest of the internet, the last thing you are going to do is advertise that fact and draw attention to yourself.
Exactly my point. How many will risk it knowing the consequence?
Internet is somewhat "blocked" in China but that doesn't stop Chinese poeple from posting around, right?
It's not that much about how effective you're blocking poeple but rather the fear poeple have from what might happen next and knowing how all windows in Rusia are deathtraps, teleporting you from your ground-floor apartment to your neighbor on the 6th and throwing you out, I wouldn't bet on poeple trying to go around it.