when we travelled Y to VIE in August, we were told No only for F and J pax only because of the number of airlines that operate out of T3.
The pleasant check-in agent said that if T3 allowed BA status PAX in so they would have to allow all the other FF programmes in as well.
He also said T3 security is much faster than T5 anyway so no problem, I agreed with him after going through so quickly.