Consolidation companies can work with collection agencies. This is normal for them. Good counselors know how to make the deal with the CAs. And you will be surprised to find that the CAs who never wanted to work with you will accept payments from the consolidation companies. Actually, most of the times, they find the customer to be an easier catch for them and they don't want to talk with some professionals. But they want to recover the money too.
Amex is making a deal to you. Should I think that they still hold your file and have not sold it off to outside CA. If you can push more, you can actually deal with Amex directly and won't have to work with Allied.