Dogie,
no Bitmain isn't using the p2pool share chain.
Right now:
Pool rate: 3.88PH/s (7.0% DOA+orphan) Share difficulty: 16500000
murraypaul:
if they were using the p2pool sharechain, they can't divide their payment up into 2 addresses in the coinbase payout.
They can pay it to themselves, as the p2pool does, and then later distribute it based on some fee/nofee calculation of course - but that of course won't be all the tx fees, just their payout % of them.
But as I said at the start of this post, they aren't using the p2pool share chain anyway.
And as you said earlier .. if they try to force some different protocol into the chain, they will fork it. Which means, still, they aren't using it.
M