Hmmm... that's quite an idea - IR at night. It's probably possible, as you can do IR portrait stuff with high - level tungsten light and a deep red filter.
As to how much IR comes from street lights, it depends on what kind of a light it is... I'll get back specifically the info for different types shortly...
And for the speed, it's hard to tell: under tungsten light, without a filter, I'd rate HIE at about ISO 80 - 100. Under daylight, it's a little under ISO 200. Using a filter, though, the speed changes quite a bit.
At night, though, with an infrared (RM72, wratten 88), the speed will proably be in the single or low double digits. Your exposure meter will also probably not give you any good information, due to poor IR sensitivity, so you'll have to guess and bracket a lot...
Try it though, this could be really neat...