The union of Muni operators (Transportation Workers Union Local 250-A, if you're hoping to identify them by their letter jackets) is suing the city, along with Muni Chief Nat Ford, to block the parts of Proposition G that they deem unfavorable to their contract negotiation process. Namely, they don't like the part where any "impasse at the bargaining table" will be solved by an independent arbitrator who must take in to account any proposed contract's "impact on fares and service."
Right, because it would be terrible to consider those of us who actually use Muni when the operators are asking for more pay. Since the union's contract is up in June, we should probably start getting worried about the possibility of a strike (which they're not technically able to do), but they're not exactly working hard as it is. And Nat Ford probably isn't too concerned, he's halfway out the door and on to bigger pay already.
[Chron]