I have Medicare B with a supplement and it covers everything at Mayo. I do have the richest supplement. If you don't have the supplement, Shands at UF takes everything. Even though Mayo says they don't accept Medicare, they will file for you. I've never had to pay a penny out-of-pocket there since being on Medicare w/supplement.
FWIW, you really need a supplement if you only have Part B. Part B will cover 80% of durable medical equipment but Supplement Plan F or G will cover the remaining 20%. The supplement has saved me tens of thousands of dollars in just two years.
I explored the advantage plans but, in Florida, they would have too many co-pays and didn't cover all of the co-pays for DME.