It would make sense that Deves would have some kind of defense against each others powers, like sensing telekinetic attacks, deflecting mental probes, or sensing incoming nearby portations. Obviously those with specializations will excel more in their sphere, in both defense and offense. Telepath Deves would be a bit more subtle, but that applies to mundanes, to other Deves it'd be more of a power thing, if a Deve was trying to keep a telepath out of their head then they might could brute force their way into obtaining whatever information they want, but the Deves don't have a lot of reason to distrust each other at the moment.

As for recognizing each other, they kind of already do that on instinct. They just know. There's a kind of psychic presence they just notice.

The whole telepathy thing is most probably passive at this point, just unconsciously stretched out, but not actually focused on reading thoughts until it's deemed important.