BHN/TWC used to be the same company, but the folks who own BHN split off the systems they owned and now they manage them separately, meaning they can offer different speed tiers, etc. The internet backbone has nothing to do with it.
said by kd6cae: Finally, should the time Warner/Comcast merge occur, will that effect Brighthouse in any way?
The answer to this is yes, but it's impossible to know *how* it will affect BHN. Over time TWC's "way of doing things" will disappear, including their separate internet infrastructure. It'll all get absorbed into Comcast. There are many outcomes (BHN could use Comcast in the same way they've used TWC, BHN could start handling all those functions on their own, BHN could sell their company) but no one knows until it happens (BHN themselves probably don't even really know what they're going to do yet for sure)