This is possible. As someone alread mentionesd, it is a breeze with a flash, as they do put out a significant quantity of IR. If you want IR only, as long as you have an IR filter over the lens, you should be good. (Another fun thing ot do is put an IR filter over the flash but not the lens so you cna take photos that are minimally intrusive to those around you). You'll have to fiddle with flash and exposure settings, though.
At night, exposures with an IR filter take an EXTREMELY long time, but it is doable. I've had exposures take minutes and still come out severely under, when a normal film would've been fine.
Without a filter, it works, but there are many films with better reciprocity.
HIE, when used near an artificial lighting source (street lamp, headlights, etc), come out VERY nice, with some interesting effects.
If you're not looking for the IR effect, go with something better (and cheaper) than HIE. Otherwise, if you'd like IR at night, give it a try, but bracket WAY more than you would during the day.