Besides real-world-authenticated PoA, bridging seems to be one of the other distinguishing fancy new features POA brings to the table.
Where can I learn more about POA bridging capabilities? My limited understanding is that it connects various ETH-based blockchains together, so ETH, ETC, EXP, POA can all talk to each other. Which is to say, a contract running on POA network can execute contract methods from other networks. How does it pay though for the execution?