I no longer live in Russia, so can't tell if it is true, but from what I'm reading, Telegram devs used a clever hack to bypass the blocking.

They say Telegram is using service PUSH notifications (DC_UPDATE - https://core.telegram.org/api/push-updates) to send new server's IP.

Apparently, those push updates come from Apple/Google/Microsoft notification servers. So if Roskomnadzor blocks those servers, then all push notifications will stop working altogether (not only for Telegram).

Does anybody know if it is possible?

Also, Roskomnadzor asked Apple/Google/Microsoft to delete Telegram app from their app stores.

UPD1: Obviously, Web version of Telegram won't work as it doesn't have/use push notifications.

UPD2: Roskomnadzor blocked ~800,000 Amazon IPs and more than 1,000,000 Google IPs. People say they're having issues with Viber calls