BTCC will consider one BTC to be equivalent to one 1MB and one 2MB.
They're two chains with different consensus rules, so they can't just be BTC. I'd rather that SegWit2x futures were traded in BTC value, and 1 BTC stays at the value of 1 BTC.Obviously SegWit2x is going to call itself BTC as well, but since it doesn't exist yet, it would make sense to compare it to something you can actually send to and withdraw from an exchange so that you can trade it with something that actually exists.
After the fork happens, exchanges could decide which one chain to call BTC based on which has the economic majority of support.