Yes, it utilizes the calling card method of dialing the number through your google voice account so that the google voice number shows up on the other person's callerid.
I didn't implement a select from the contacts list of the Google voice number on the GV Info pivot screen. Rather, you have to type in the number using the numeric pad and input the pin that Google Voice prompts you for when you access your account. After you've placed both the Google voice number and the pin, then you can select the radio button for that account.
As far as I know, GV direct dial only works with the accounts that you can specify the phone number with. Currently, you can only use a phone number with two different accounts. The calling card method is the only one that I know of to use one cell phone number with three or more different accounts.