From my electronics/Avionics days to my more recent computer days I have come to believe acronyms will be the downfall of communication and peace in the world. It is Babylon all over again. That is why I define most and in the future probably more of any acronyms I use.
It is apparent that your last post that mentions 70 sites / 40 sites and is vague about applications is extremely different than your first post 1 company and 2 wan providers.
However having read your post a few more times (following Sahirh’s advice) and scratched my head even more bald than it was. If you are saying what I think you are saying. I would remind you that EIGRP is an internal routing protocol. This means it is perfectly understandable that one autonomous system (WAN provider?) would not want to share with another (WAN provider or Company).
I suggest you use BGP. Of course that is only if you are saying what I think you are saying. That is you are talking about three different companies (autonomous systems).
Like Sahirh, much of this one is over my head. Except that I'm going through a WAN transition (albeit much smaller) from one technology/supplier to another. Because the WAN is business critical we have to run both in tandem for an overlap period, and the way the new supplier is doing it is to use BGP with OSPF. The new WAN runs BGP, the old one just OSPF. And the BGP is set up to inject the necessary routes back into the old OSPF to keep it all running until it can all be changed over