I did a little experiment with a throttled Sympatico login, to plot a timeline of when the throttling occurs. I downloaded and seeded a torrent, with lots of downloaders so the upstream usage was quite steady.
I tested the upstream not downstream, I just didnt want to waste so much bandwidth over a 24hr period. But I think they get throttled equally. Here are the results.
Traffic shaping timeline (upstream)
2am-4pm - Unrestricted upstream 80KB/sec
4pm-6pm - Upstream starts to drop to around 60-65KB/sec
6pm-12am - Upstream gets throttled heavily around 35KB/sec
12am-1am - Upstream drops a bit more below 30KB/sec
1am-2am - Upstream goes back to about 60-65KB/sec
2am-4pm - Unrestricted upstream 80KB/sec
Keep in mind those are upload speeds, but I suspect a similar timeline is used for downloads. It's just after 8pm and I'm seeing my downloads seemingly capped at 30KB/s. My maximum download speed is about 510KB/s.

