I work for JCOM. I don't publish this info publically on the boards, so don't broad cast it.
In limited areas we have a pure fiber service. Currently our network is a mix of fiber and cable. The main trunk between your neighborhood and our local center is fiber, but cable to the individual houses. If you are lucky it is all fiber.
The standard internet service is 160M plan or 160mbps down. This is the rate for the implentation of cable standards. Your actual rate should be around 70mbps. Plenty for 1080p streaming etc. We are rolling out 360mbps service in many areas now. The guys around me are always making announcements what the have done regarding the 360m upgrade that day. The main reason it takes so long is we do tons and tons of beta testing for everything.
I work as an engineer but in an unrelated department. I have asked a question about throttling before to someone. I got a vague answer at the time, that it does happen but it is not common. I have not confirmed but based on the reasoning below you can avoid it and still torrent. JCOM doesn't really look at the ports or the protocols going through.
The reason is nothing to do with copyright. But because the upload bandwith is limited. Taking a large amount of upload bandwidth for a long extended period of time affects others on the network, or should I say people under the same node (i.e. your neighbors).
This affects other paying customers and then they complain, and Japanese people love to complain to businesses.
I have not 100% confirmed the throttling but based on the answer I got that is how it happens. Watching your upload should help you avoid it.
Most cable companies only implement DOCSIS2.0 which is why their download speeds are so slow. we implement a kind of combination between ver 3 and 2. We allot many download channels (frequencies for downloading) but not for uploading. This is done since most people prioritize download speed. We can't just allot more upload channels as not only does that mean buying supported equipment and lots of testing but other frequencies are used for cable tv, earthquake alert system, etc. We are working on expanding our frequency range so we can have more room to stuff more upload and download channels.