is every engineering branch in IIT good enough to obtain placement in reputed companies or govt. sectors?

Hi..
The placement is not only dependent on the college you are studying in..
What IITs do is that they will provide you the best opportunities to get good placements. It actually depends on the individuals how they want to make use of the opportunities given to you.
Ya, every branch in IIT doesn’t offer you very good placement. But, if you are expertise in your field, you can grab any number of opportunities.
Have faith in your skills and try to give your best.
Regards