a) It appears that the side chains cannot offer any block rewards.
b) They would need to achieve a certain level of hashing power.
I am not sure how b) would be possible without a)
c) Another note, I read elsewhere is that. The value of the 'betacoin' on the side chain can never exceed 1 BTC. As coins can always be moved from the Bitcoin blockchain into the side chain.
While this seems like a nice way to experiment. I am not sure what are the incentives for the AltCoin developers (zero profit).
If someone more technical can review the details and post a ELI5 that would be great.