This is a difficult level. Here’s how to scrap through the level:
What I did was to basically recruit as many of the locals as possible. Order down some more transports. Make sure the TR-MB does not initially get damaged in any way.
Look for good areas where you can get the first prisoner and where you are not in the line of fire with the turrets. Get hold of the first prisoner. It's best to first send in the transports so that they attack it & not automatically kill off your troops. Put the prisoner into the transport. Use the grenades to kill the rest. It might be better to work out how to fast select units and its second ability.
Do the same for the main prisoner. You may be able to retreat and save some units? Go down through the valley. The first prisoner actually goes into one of the neutral buildings. Here you can order a couple more transports.
Next Order the rest of the group to attack the turrets on the left. As they are doing that then JUST MAKE A RUN FOR IT! Have any remaining units follow you. You will lose health fast.
Somehow I just made it with only about 10 health points! There is probably a much better way to do did, but this worked for me.