To your point about doing IPTV over DOCSIS - you need to have a pretty small node size to do this, by my estimation. If you want to deliver 4 HD streams to a house and fast Internet, that adds up to a lot of bandwidth pretty fast. Too many houses on a node and it just can't be done.
How is this true - the broadcast from Shaw already delivers all of this content to your house simultaneously, how would it be different if the delivery method was IP based? A standard CATV system of 125 channels could deliver 38Mbps per channel. At 125 channels this equates to 4750 Mbps.
Granted the return path is something to be contended with as is the infrastructure required to create that many DOCSIS channels per node but it is theoretically possible.