SneakyPolarBearRoamer spawns spy and disguises as medic, takes out sapper, and hits B. Tells you what medigun they are using. If you are fast, you can reach mid at the normal time (one medibeam length in front of your medic).
Your team runs kritz to mid regardless of their medigun.
If they QF, then you don't go to mid and just defend 2nd/yard. Get a pick and then just kritz into them or just wait for them to push you and kritz then.
If they run uber or kritz, go to mid and fight normally just like any other mid. If they are on uber obviously play with your demo passively and hope to get kritz fast and win mid with that. If they are on kritz its pretty much even, not much strategy you can have.
We did this in our match against pot's team and won two rounds in a row before they switched back to uber. You just can't win mids against an equal team if they run the QF and you don't.
Med can spawn with quickfix and then on the cabinet tap change to medigun