As many of you know, Hawken is not the most forgiving game and this can lead to people leaving mid game. When this happens the game lets everyone on the opposing team know that the teams are uneven and asks for volunteers to switch. This is great, except the part where there doesn't seem to be a binding listed in the notification text. Many assume that you cannot volunteer for team switching because the notification doesn't tell you which button to use.
Well, I found it while playing earlier today. If you would like to switch teams when the game is asking for volunteers.
Press down on the D-Pad.
This will add you to a list of willing volunteers. The best match out of that list is then switched to the other team after a short time. If no volunteers are in the list. The game will look for the best fit on the opposing team to automatically switch over. This doesn't always work though, as it won't switch someone who hasn't died yet. Volunteering for switching teams keeps games even, will reward you with a badge, and some HC (150 I think) as a thank you every time you switch.
Hope this information helps!