I just spent the last 40 minutes on the phone with ccbill as we are in the process of adding up-sales within our program to the join forms. The following is not currently an option for cross-sales (sales to a different program).
CCBill program owners can enable "Share Extras" for up-sales within their own programs to ensure that affiliates get the same % on up-sales as they get on the sale itself. More product sold means more money for everybody!
GMPcash will always have this option enabled when up-sales appear on our join forms. We have no plans to add cross-sales to the join forms.
It might be a good idea to ask a program owner how they handle this before deciding whether to promote them or not. Bear in mind that some ccbill program owners may not know how they are setup and a gentle nudge may get them pointed in the right direction. After all, it took me 40 minutes and a test sale to prove that it works.
Thanks for asking the question as it got me thinking - and made me search for the answers.
I do agree with Toby - I never promote tours that have review site leaks all over the program tour for the same reasons.