Forgive me if I'm wrong, but no, TCAS doesn't work (completely) with Mode C. The airliners will get a TA (traffic advisory - tells the pilot there's traffic, but won't tell him what to do about it) if the traffic has Mode C, but not an RA (resolution advisory - which tells the pilot to climb or descend, after negotiating with the Mode S transponder in the other aircraft).
I want to make it clear that I do not think this is a valid reason for installing Mode S in all GA aircraft! But we need to get our facts right if we're going to complain.
As for not squawking Mode C, the only time I've ever heard this is when I've been told to squawk Standby when approaching airfields like White Waltham which lie on the edge of busy airspace - and that's to avoid cluttering up the ATC screens, not because of TCAS. But, having spoken to the controllers at Heathrow about this subject, I will now continue to squawk Mode C until I'm off the runway. I have been told not to squawk Mode A because of TCAS - I believe that pilots will be given a TA for any traffic in the same area if the traffic is squawking Mode A and not Mode C, even though the airliner is probably over 30,000 higher than the other traffic.
Apoligies if anything I've said in this thread is wrong... it's been about 6 months since I did the exams, and I've forgotten lots since then! I'm sure someone will put me right if necessary though...
FFF
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