another technique you can use, if the engineers are ai and not player controlled, is just to "cheat" the clearing.
I am assuming you can create and call the engineer team, so to the minefield:
move them there...
when they arrive activate a countdown, say 2 or 3 mins
after the countdown, deletevehicle the mines, viola! no minefield
bad part, you have to name the mines so they can be deletevehicle
not really realistic, but should be efficient
good part..much less scripting.
I have discovered that ai engineers can be ordered to deactivate a mine by a player groupleader if they are standing really close to it.....
does this help?