Renae, I don't have personal experience with the Marsh Program for photographers but I am familiar with the players:
Marsh is a broker (someone who obtains insurance for another person and supposedly represents the person, not the company) but they are very tight with their insurance carriers.
My understanding is that the policy is actually written by Lexington Insurance Company, a member of the AIG group. Now before you get your undies bunched, AIG's insurance group is completely liquid and probably kept their financial division afloat for longer than they should have but, my experience (and I worked for AIG claims for a short period) is that they are not the strongest customer service company around.
And when you refer to York, I'm guessing you're referring to York Claims
[
http://www.yorkclaims.com/YCS/ ]. If so, they are a big independent adjusting company that started in the northeast (where Marsh McClennan is located in NY and Lexington is also NE based) so they don't have policies - they have to get them from the company.
This is often not the most efficient (and often very overloaded/overworked) set up in insurance. Having said that, I'd be highly surprised if PPA would continue to endorse them if you experience is typical ... and if it is, then PPA needs to hear about it.