Ruslan
I think you will find that if the Russian TCAS was not working the 757 would STILL get a TCAS RA provided the transponder was OK on both a/c, what would NOT happen is the aircraft co-ordinating with each others TCAS so that they did not BOTH call a descent, but as I said, at the momment we only know that there was ONE (757?) TCAS warning, ANYTHING else is pure conjecture (don't mind the what ifs, but some people have been STATING, if they had done this they would not have collided, far to definate a statement at this stage).