AIR was never meant for Catalog replication. It replicates the backup images and updates remote master server with relevant catalog entries.
This means that there is no need for catalog backup replication. Catalogs are already updated with the Import job on the remote master.
About AIR replication between different NBU versions -
the following has been in Admin Guide all along. (extract from 8.2 Admin Guide I):
The ability to perform Auto Image Replication between different versions of NetBackup does not overrule the basic image compatibility rules. For example, a database backup that was taken in one NetBackup domain can be replicated to a NetBackup domain of an earlier version. However, the older server may not be able to successfully restore from the newer image.
You can't AIR images that have already been taken and have not had AIR operation configured as part of the relevant SLP.
Basically, AIR cannot be applied to images retrospectively and this is by design, so the short answer is no for existing images.
For new images it should work as long as both versions understand the format (i.e. no new policy types etc)
Actually, nbreplicate can be used to do this as long as there is an SLP configured. There is some discussion ongoing as to the supportability of this en masse but it is being discussed internally whether this is supported and documenting it as such.