As arrogant and air-headed as dealership service departments can be I'd hate to think of some of them having to do anything outside the norm. Even to get paid. Though it's hard to understand a dealership (auto) or otherwise thinking they had no incentive to make the call to a warranty provider. The incentive is getting paid for the work. Why do they care who is paying the bill; only that it gets paid.
The difference Don is that the dealer didn't sell the plan to you while making a fat commission like he does on the H-D plan, so many of these business geniuses take the nearsighted view and blow you off. They can't blow you off with the H-D plan, but with an independent plan if they want to be jerks (and who among us hasn't run into several Harley establishments that just love to be jerkish?) they could just tell the customer to pay the bill and take up reimbursement directly with the service plan folks. As someone else noted, it's a similar situation to taking your medical or dental plan to a non-participating doctor or dentist. Some will still submit your claims for you but won't accept the negotiated prices, while others won't even submit the claims for you.
As for getting paid for the work, most states have a little thing called a mechanic's lien that assures them of getting paid if you ever want to see your bike again. Once you hand the bike over and sign the authorization on the work order, they've got you. You want your bike back? Pay up, and we'll be happy to hand over the keys and even roll it outside for you.
Before purchasing any service agreement the potential consumer needs to get answers to important questions like who are the participating repair establishments in your area, what do I do when traveling outside my area, do you pay full retail prices for repairs by non-participating establishments, etc.
Jerry