ULA-C sounds to me like a request to the guys who spin silicon to help people keep from screwing up their router configs. If someone can't manage to filter their BGP such that they keep some (or all) of their space private, I don't see why Cisco, Juniper, et al., need to do that for them.
or that the router vendors will do a more reliable job of it, given the complexity of knowing what is a site border and what is not, especially when folk are saying that there are actually multiple entities inside the border. and do we really want the vendors to hard-code address filters in the sillycone? this is the path on which site-local died, and the death was a good thing. RFC 1925 2(11) “Every old idea will be proposed again with a different name and a different presentation, regardless of whether it works.” randy