On my last KQ flight I saw priority Immigration at JKIA for arrival and departure.

For departure there is a separate manned lane that feeds to the front of the "normal" lines. On arrival there was a separate lane, but when KQ 101 landed from LHR, the Immigration official took his break. On the plane they give you so called Fast Track cards on arrival into Nairobi.

Ex. Mombasa where the boarding cards are collected to board, there is a separate lane for J class and Elite Plus. As we were in the lounge, I don't know how effective this lane was.

But checkin at JKIA International for J class is a pathetic. You can queue for up to 15 minutes. The lounge sucks. Hopefully with T4 opening next year, KQ get access to more lounge space.