Bitcoin ABC (or whatever its name) should fork like hour ago.
But as far we can see, there is NO new block using new transaction format, so ABC node is accepting "normal" BTC blocks.
Hardfork will happen, when ABC miners will mine block that is using new transaction format (that is incompatible witch normal Bitcoin) or block will be larger than 1MB.
So far, we have indication that ABC miners have around 5% of total BTC hashing power, so 1st HB block should be online in 200 minutes (3 hours). But this is NOT sure, because all numbers are hypothetical and statistical.
So, as far ABC miners not have "own" block, ABC nodes are accepting "normal" BTC blocks. When they finally hit ABC block, it will be first block of new chain. Next ABC block will be build on this.
ABC have changed its diff regulation, every block is checked that there is less that 12 hours gap between blocks. If it takes too long, difficulty is cut by 20%.