Is that PH as in Plane Handling ?? , because Aviance already own Plane Handling
'Own' ... yes, but they operate separately and independantly. I think that I read something on the side of one of their tugs ... something about being 'part of the Go-Ahead Group'.
From what I've seen, they don't use each others people or equipment for their own flights, so they would seem to be separate.
Also, from what I've seen 'out the window' PH only seem to do larger aircraft types (747s, A340s, etc) while Aviance do a lot of smaller types also. I'm sure the "'who handles who" thread will have some answers.