So far transit officials have chalked up threats of a Muni sickout as nothing more than a rumor. But that doesn’t mean they aren’t prepping for the worst.

The San Francisco Municipal Transportation Agency blasted off a memo of its response to a flier that is cooking to plan a sickout starting Monday. Paul Rose, spokesman for the agency, said it’s not possible to supplant a transit service with more than 700,000 boardings a day in the event of a sickout.

Still, they are tapping BART and other regional transit agencies for help — just in case. And if it comes down to it:  “We will consider a way to use taxi cabs in The City,” Rose said.

However, transit officials are still dubious of this planned sickout saying nobody has claimed to organize it. ”The bottom line is we believe our operators understand how important our system is to our city and believe they will do the right thing.”