[Onramp]

Depending on how many people are watching any given channel on any given fibre node, the rest of the bandwidth available would fluctuate. This will probably happen (is happening?) eventually.

At the moment it's simpler to spray every channel down every fibre simultaneously (with the exception of some on-demand stuff).

The channels are already delivered via multicast from the super headend on the vm backbone, it's just the regional headends (as far as I know) that are streaming these channels via IP multicast with receivers there (at the regional headend) - and then modulate them all to RF channels in groups for transmission to all the nodes simultaneously.

In theory if nobody is watching a particular channel on a particular node, that RF frequency could be used for data instead until one of the subscribers tunes back into it for TV purposes. There would be similar ways of doing this also (but over DOCSIS) but you probably don't gain a huge amount.

The more segmented the network, the more you could get away with reusing TV bandwidth for data (even if that data is for streaming a particular channel over multicast temporarily) depending on who's looking.