Recovery is something that is loosely defined in the current specifications. Only top-down recovery will be supported in the GA version of TS 4.2.1. There will also be the assumption that participants fail and recover on the same URI. That limitation will be removed once we move to the new specifications, sometime towards the end of this year.
You say "Only top-down recovery will be supported in the GA version of TS 4.2.1". Am I to infer from this that top down recovery is not supported in the BETA version of TS 4.2.1?
If it is supported, how do i enable it?
It's not in the beta release. You won't have to do anything to enable it when it is there.