I often use ventrilo when I play EIB online with my brother and it makes the game MUCH more enjoyable.
I think it might become much more complicated in Hell's Highway though with lots of different people playing. Giving out your ventrilo/teampspeak/whatever channel information to any new teammates and waiting for the to connect before each mach would be a HUGE pain in the ***.
Why not build something into the game where anything that goes into your mic input comes out on your teammates' speakers/headphones? This way people are automatically connected, and even people without a mic can hear what there teamates are saying which can be very helpful in coordination.