Every time I have come out of Stonebridge Park Depot e.g. service 201D-01 the signal WS-38 is always showing red but actually seems to be green. You can drive right through it. I hunted around in the grass to see if there was a hidden shunting signal but there doesn't seem to be one. On the map is shows as green. I've tried it on several scenarios and it always seems to be this way.
If in doubt, contact the dispatcher. If it says "Denied. Wait for the signal to change.", You know it's really red. If it says "Proceed as signals indicate", it's worth giving it a try!
I've been knocked out of the game doing that. Proceed as indicated means don't proceed when its red . I find its nearly always right on the F9 map so rely on this if not sure.