It's not unheard of and as you say wearing the old hats is particular popular with the Scots infantry but for most regiments it's very much an other-ranks thing. Most former Cavalry officers are far more likely to be wearing a bowler hat on Nov11 rather then their old berets.
I caveat this with the fact that it was the Royal Signals TA and they do love their dressing up.....
When the reorganization of the TA put a Liverpool based sqn in 32 Sig Regt, the TA Sqn Commander decided to adopt the Scottish hat and styled them as 'Liverpool Scottish' which really upset people for obvious reasons. Fortunately it only lasted a few years before they moved back to berets.
https://www.youtube.com/watch?v=tOVQap9GC_U