That's not familiar as a concept in Germany. It's up to the individual driver to drink no more than 1 beer (well, a Bavarian Mass might already be too much...) or to have someone sober who drives back, but nobody will ask. But I'm sure police are very strict especially during Oktoberfest season.
BTW, your picture is from the Hippodrom, I guess, it's not the biggest tent of Oktoberfest, 3,300 seats. (Edit: just checked, the Hacker Pschorr tent has 7,000 seats.)
http://www.hippodrom-oktoberfest.de/en/