I believe this an exploit but I am not totally sure. Here it goes:
1. Get the mechano-hog.
2. Mount up in the first room of WSG. (You can do that on beta).
3. Get a skilled player to jump into the side car of your hog. (He will be the backup).
4. Drive all the way to the opponents tunnel and try to jump just as you enter the tunnel.
5. If you were lucky you will be able to drive the hog ALL the way up the tunnel and into the flag room. There you can pickup the flag JUST BY DRIVING OVER IT.
6. Turn around and drive back down the TUNNEL back towards base.
7. Cross the field in the hog and try to do the jumping thing at the entrance to your tunnel.
8. Drive over your flag with the enemy flag.
9. You capped a flag. Rinse.
10. Repeat.
11. ???
12. Profit
Although I am not sure that this is an exploit. It could be working as intented. It is EXTREMELY similar to HALO. Driving the loud warthog from base to base capping the flags quickly.
NOTE: Sometimes you get dismounted when you enter the tunnel. Fear not. This is where the back up comes into play. If you for some reason cannot mount all the way to the opponents flag. No worries. Just have your backup pickup the flag and then you mount up on your hog and he can STILL click on your hog to hop into the side of it. Then you can drive him home.
Hopefully this isn't a repost. Peace.
If you guys need clarification or have questions feel free to post.