How long's the event? Giving everyone two liters of beer over a couple of hours seems like a pretty awful idea unless there are cheap / free DD tickets.
I walked into Brewer's last year when they were holding one of these events. I didn't have tickets but still was able to sit at the bar and have beers like normal. I don't think they close the restaurant, so a DD could go without buying a ticket (assuming I'm correct). There's also virtually no parking there anyways, and it's a close walk to the T at North Station.
The North Station T is a mile away from Brewer's Fork. I am not sure I'd call that a close walk, but it's all relative, I'm sure.
If you thought four lagers over a couple hours is a bad idea, Extra Dirty in the North End is worse. Just went to Red Fox the other night, nice place. “To score a plush seat at Extra Dirty, customers pre-pay for tickets that cost $90 apiece. Each ticket includes an aperitivo, three cocktails, and three plates of food, plus a little sweet bite at the end. As the space is small — 20 seats in total — Extra Dirty keeps each booking to a time limit of 110 minutes.”
Found out a little more about the event. The restaurant will be open to the public. All the beers will be available on tap to anyone. The event runs from 2-5 but it sounds like you can drink the beers over any period of time if the restaurant is open.