MOCA has several bands. IF the provider is using up to 1 Ghz, they should probably use MOCA band D so it doesn't interfere.
Slide from this presentaion:
Verizon didn't start with 1 Ghz because at the time they launched, the boxes weren't available to do 1 Ghz. It's possible now, but doesn't provide a huge benefit for the costs involved. Especially since all the 1 Ghz capable boxes also do MPEG4.