I think Comcast would be pretty opposed to let a competing product into their not-for-sale DC space. The real benefit here is that it saves ISPs on peering charges. Comcast, AFAIK, does a lot of their own peering and has financial motivations to NOT let Netflix into their DCs (onDemand.)
We will see how this plays into the me neutrality battle...
Comcast does not operate their own video delivery infrastructure. They contract that out to Akamai. Furthermore, Comcast will happily sell non-transit, A.K.A. paid peering, to all who come. They don't (and never have) sell colocation (DC space). Presumably, Netflix is just going to buy access to the Comcast network, same as every other CDN has done.
We will see how this plays into the me neutrality battle...