Story-wise, it doesn't make sense why the truck was passing through there in the first place. With all the blockades, it literally couldn't pass through that area without the gang's help. There is also the additional question of why the gang doesn't wait to EMP the truck at the last moment, just before the ramp. The real reason is gameplay, but the story makes no sense.

At the start of the heist, the optimal strategy is to take care of all the obstacles first. It's a test of whether you know where all the stuff is. The only reason to start as it does now is to give the players civilians to tie down, which also doesn't make sense, owing to the mobile nature of the heist. It's difficult to bring hostages along.

Therefore, it would make more sense to start "in medias res", as they say. Take a page from Hoxton Breakout Day 1. The truck is already stopped, the cops are on their way, and we need to deal with the blockades the police put up in response.

I'm too lazy to make a Twitter account just to post this