VM's coxial/HFC is easily capable enough of supplying a 1Gb connection if they wanted to.
In fact they could give you 1200Mb down and 216Mb up - however this would mean having to kick everyone else off your local node as that is the total amount of bandwidth that is currently shared on areas with 24 channels.
VM have, at most, 6 upstream channels active in an area, not 8, and they only allow bonding of 4.
24 channels is rare. 32 is a more common number now.
Gigabit will probably have to wait for DOCSIS 3.1 which isn't that far away now.
Building better networks, not just faster ones.