There's no typical response. Here in QWest territory they drop their own
cabinet and pull AC power for their own rectifiers and battery string
inside the cabinet. (I helped lump the freaking batteries oy...)
The corollary to this question:
If your data center has an adequate DC plant, will the carriers insist
on installing their own batteries and rectifiers? And how many of them
have redundant supplies to take advantage of an A and B feed from you?