There are several priority codes that que a pax/non-rev in a predetermined priority
There are several different codes for upgrading, for example Plat Elites are ahead of Gold Elites, Gold Elites are ahead of Silver Elites, Companion upgrades (even for Plat Elite Companions waiting for a gate upgrade) are after silver elites, and "mishandled pax" are after companions, then non-revs are last, in a predetermined order.
However, all these pax are put on the same list, just in a different sequence. I asked Beth about this and she emailed me in May with a more detailed explanation. It is all one list.
RC