AFAIK, URP members are PDIC, IDEA, SSI(NASDS), NAUI and YMCA(SEI)
If I send someone to a URP member instructor, I can depend on their getting the qualification dives per the program - that is, they can use the tables or computer they already know and don't have to take any additional written test. The referral paperwork comes back to me, goes into the student training record and the student gets their c-card through the referring (our) shop.
If I send someone to PADI, all bets are off - they may get the qual dives per the program... or ... they may be told their training is worth nothing and they must pay for and take the entire PADI course, or anything in between. For this reason I will only refer a student to a PADI instructor when PADI is the only agency who has instructors at the student's destination, and I do my very best to get the referral instructor to tell me in advance what's going to be required. I have had very bad experiences with PADI and referrals - been told the student will get the qual dives per the program only to have the student get popped for the cost of a full PADI course, have to take the PADI written and get issued a PADI c-card after the qual dives.
What I don't know is whether PADI has recently joined the URP (I doubt they have), or whether PADI has issued any official policy statement to their instructors on participation in the URP. From the posts in this thread it is apparent that there is still great confusion among PADI instructors on how the URP is supposed to work.
Rick