Appears to depend on whether there's a central security checkpoint or gate security checkpoints.
A relevant discussion here
http://www.pprune.org/passengers-slf...assengers.html.
The issue is not whether one SHOULD be able to mix with outbound passengers on arrival, but the fact that MAN airport DOESN'T want this to happen (hence putting us behind a glass wall and sending us through tunnels) and nevertheless tolerating a situation where inbound WCHRs CAN mix with outbound pax