Ignition would know
Based on recent events it would seem a particular CMTS has lots of line cards and lots and lots of gigabit ethernet ports. Making distinctions on the CMTS level aren't really useful. Links from the CMTS to the core are rarely if ever congested, because there is so much more of it than capacity from the CMTS to the end user.
What you really want to look at is line cards and congestion at that level. There may be multiple line cards serving an optical node and subcabinets from there. Not every customer on any given cabinet will be connected to any given line card, a line card's capacity may be spread over several cabinets, and have several line cards serving each cabinet. How granular this actually gets I don't know. But it's not the case where everyone on one cabinet => one set of capacity.