I'll go for a week or so with nice steady pings in the 45 range and then I see something like this for a few days. I am served out of the West Street CO in lower Manhattan which is still undergoing repairs from Sandy. Could that be the issue?
Well, I've been in this position many years ago when I lived in a college apartment complex and we would overload the upload on our nodes after 35/35 came out pretty much constantly. I called and complained along with some of my friends that lived there at least once a week. It took them about 6 months but they finally added capacity in the complex and it was never an issue again. (At least while I still lived there)
The techs can at least open a report on your issue for engineering to check out, but most will tell you after the report is filed nothing can be done. We just harassed them until they got the extra capacity installed because most of us are gamers and we can't stand the bad ping.