There are some misunderstanding in your words. If you mean 1 server and 2 different PGs on it for your instances - yes it will work. If u mean 1 PG on 1 server for serving 2 instances - no, it will not work, as Ed said.
So you could certainly have a PG1A for instance 0, and PG1A for instance #1, running on the same server. They can absolutely connect to two different sets of central controllers. The instance numbers selected determine the range of TCP/IP ports used by the services. So long as there's no conflicts, you should be all set.
They could even both be talking to the same ACD, assuming its CTI links support it. You would definitely need to ensure the ACD & ICM configs don't overlap. Instance 0 would monitor trunks A, B, and C, and skills D, E, and F, and instance 1 would monitor trunk groups G, H, and I, and skills J, K, and L.