Btw, my brother is a network engineer working for a cable company. Hence how I've heard about some of those things. Among other things the cable company probably doesn't want you to know. Like how [bit of uncertainty here of details] your cable modem actually keeps track of bandwidth usage, and sends the logs everyday at some preset time to the cable provider. At least with the old modems I've heard that power cycling them will make them forget. So if you power cycle your modem just before it's supposed to send it's logs, it will register as no bandwidth used for that day. I don't know for sure if that really works as I've never tested it, nor am I really sure how to test it. Plus it sounds like a really dumb way to operate, so I can't imagine why it'd be done that way. But hey, I've heard of worse.
Hmm, I've never heard of that (at least in the US, maybe different depending on different parts of the world).
I know in the US, most cable modems use the DOCSIS standard. It defines how the cable modem is to connect to the system. Probably the most important thing that it changed from old modems was the way it throttled bandwidth.
During modem boot-up, it connects to the ISP's gateway server using TFTP and downloads a configuration file. This file gives the operating parameters to the modem, including the maximum transmit / receive rates. (Basically, a different config file is selected based on what service tier you're paying for).
On most modems, this is always read from the network (coax side of the modem) and cannot be replaced by the user. On certain modem (like the Motorola Surfboard, probably others), if the modem is booted up before the coax cable is connected to the modem, it will try to download the config file from a TFTP server on the LAN (ethernet) side of the modem. This is one way people "uncap" their modem (get the ISP's config file and transmit a modified version of it to the modem to allow for faster speeds).
I have also heard from people who work for the cable company that it is next to impossible for the ISP to detect uncapping (usage of service above the speed being paid for), since the way cable systems are setup (bandwidth is shared among all users in a certain neighborhood / area). This way, if you uncapped a little bit (say you set your cap to that of the highest tier service), it would look normal to the ISP. (If you started going wild and setting the cap to ten or fifty times the normal data rate is, then you're in for some trouble since that would create a noticeable difference).
I've never heard of logs being transmitted though. I know when I had cable internet my modem kept basic logs (which you could read through the config page) regarding connection and line status (stuff like sync being established, signal-to-noise levels, etc). There was nothing regarding bandwidth usage that I could see (I don't think the logs got transmitted to the ISP either).
(note: regarding the uncapping discussion above -- uncapping is theft of services and is illegal. If the ISP does catch you, they will probably terminate your service and possibly may want to take you to court to try and get restitution for the extra bandwidth you 'stole').