They would certainly block out all that noise. It's the whole reason I use my IEMs when I practice and not my cans. The sound from IEMs feels like it comes from inside your head rather than air from the outside, if you know what I mean.. I'm not the best at describing things. They're a whole different creature and some people just don't like them.
I'd go for a cheap pair of IEMs before dropping the money on a custom moulded set if you've never used them before.
I have a pair of Atrios from Future Sonics that I've used to listen to MP3 files on a portable player. I tried plugging these into the headphone jack but they couldn't handle the low frequencies. Maybe I need to hook them up in a different way? These have the double rubber flanges so I doubt they cancel that much noise, at least not as much as custom molded IEMs.