Re: Cable/Telco companies are LIARS.....
True about the limit bandwidth availability in the actual cables themselves, but at least with cable modem technology (DOCSIS), the TV channels and the cable modem service don't share the same bandwidth.
In cable systems, each TV channel occupies a certain frequency spectrum, which could be analogized to lanes on a road. Each channel stays in its own lane. The cable modems also use the equivalent of 1 channel (not each, they all share). If more capacity is needed on a cable wiring system, like a single neighborhood for example, additional single channels can be allocated to cable modems instead of TV channels. This is not a dynamic or shared process, though.
In the USA, cable channels are 6.4mHz in width, (it is 8mHz over by you folks, I believe) which equates to about 35mbps (varies depending on other factors). So, all modems on the same channel share that 35mbps. If more is needed, which it is, more channels add more instances of 35mbps capacity. Modern cable modem systems allow these 35mbps blocks to be aggregated together to allow single instances of data transfer in excess of 35mbps.
TL;DR
TV channels and cable modem service do not impinge on one another directly, but there is some indirect correlation and consideration.