Harold I referred to that article 210.4(C) but ex2 says it is OK to have a L/L load on a multiwire circuit if you have a 2 pole breaker.
The biggest issue will be the FLA of the condenser. If it is more than 10, that is the deal breaker. You also have the problem that even a 10a condenser probably needs more than a 20a breaker to start reliably.
Reno has the answer. Run a slightly larger feeder and use a disconnect box with a panelboard that would handle both circuits.
