So the max score glitch is actually possible in Heist Almighty. This secret island is the only place where the rocket launcher can be obtained (and only in this level of Liberty City). And park police car between two "pylons" is to prevent respawned cop from suicide. To get a glitch you have to jump into the water, turn character a bit and shoot a rocket towards the car right before you die. That means that max score glitch can be performed in other levels too.