(Wikipost) BA ARRIVAL fast track vouchers
 

CONCLUSION

From a recent trip with Iberia arriving to terminal 5, I recall:

- There is a BA ground agent manned the T5 fast track.
- On her desk there is no voucher at all.
- The mobile Iberia Business Class boarding pass is accepted.
- IB do not hand fast track voucher to any customers as they don't have one.
- As someone said, the fast track queue is slower than the normal one, it is up to your discretion whether you use it or not.

I would leave this on a wiki in case there is someone seeking for this particular information in the future.