Linux has added a concept called file capabilities. This allows certain binaries to perform specific privileged functions without requiring SUID root.
# getcap /bin/ping
/bin/ping = cap_net_raw+ep
Rsync should be able to (optionally of course) copy these attributes as it can copy xattrs and ACLs. They should also be storable via --fake-super on non-Linux systems.
Nevermind. Apparently --xattrs covers this. I didn't think it did.