Dear aspirant,

Usually Gate qualified IIT Mtech students are recruited by private companies and foreign companies like Indian oil, Shell,BHEL,GEIL,HPCL etc etc the list goes on and on. Yes a gate qualified candidate in any field related to communication systems can easily get a job in BSNL. The issue with governement jobs is that it's limoted number and there are reservations. If you are a general class candidate, it may be a bit hard for you.

As for the first part of your question, we have an entire article dedicated to it. Please open the link in a new tab and go through it. There you can find all the companies and the posts for which they recruit people.

https://engineering.careers360.com/articles/gate-qualified-multiple-options-for-you

Scope of IT branch is no less than CSE, if you are an expert in it. Yes, government jobs are there for IT students as now, everything is being digitalized. So, every office needs techies for improving and upgrading their old systems. You can also do MTech with specializations in IITs after cracking GATE.