it's been a bit, but last time I checked, mages (casters and phys ads) of various stripes could initiate together if memory serves. is this still accurate ?

I believe that the only time they can initiate together is if they are members of the same maical group (like a club). Also, being part of a group, and going by the groups laws and restrictions, I think they can save on karma and nuyen cost. Though the cost is probably (somewhat) mitigated by the fact that they generally have to pay dues.

As long as they are a part of the same magical group, it's flowers and nuyen forever.

Except that most of the groups have restrictions like "Limited membership: One single god-awful tradition."

So you create your own group out of the Awakened characters at your table. If they're different traditions, though, it makes the group formation harder. Also, I seem to recall somebody saying that an adept's Way (Warrior's Way, Invisible Way, etc.) counts as a tradition for this purpose.