Since VOIP went to great lengths to get unregulated status, I don't understand why they would have any standing with a regulatory agency. AFAIK, ISPs are not regulated either.
It is my understanding a business can pick and choose what vendors it wants to carry and what customers it wants to serve. A supermarket can freely pick and choose what brands it sells; it is not compelled to give shelf space to every particular brand or every particular food out there. Supermarkets are free to give preference in terms of price and product placement of their own house brands, and not even carry competitors if they choose.
Accordingly, if an ISP wants to sell its own VOIP service, why should it be mandated to carry any others? The only factor would be customer acceptance.
For VOIPS to go running crying to the FCC is hypocritical. They want free market when it suits them, but then regulation when they discover some aspects of the free market isn't to their liking.