Sorry for the delay - Thursday was a travel day with work. up at 4am back home at 10pm. :) That meant yesterday I got to catch up.
Because of the cross-girders and construction of the base, the troopers won't see you 'til you are at medium range. It's unlikely that you'd get a surprise round -- but I'd be willing to let the dice decide that (perhaps with a stealth roll?) If someone is good at being sneaky they might be able to guide you guys sufficiently close enough you could charge in and take them by surprise.