As far as I know it's still issue boots only during basic training. The only way that you'll be able to wear something else is if you get injured and the doctor writes you a chit. Most phase 2 establishments follow the same rule as well. Beyond that it's up to individual Unit policy.
So, if you got a testicle stamped on and had to have it removed and you were wearing your Ann summers thong instead of issue airtex shreddies, the MOD wouldnt pay up?
I think the risk assesment governing the activity that led to your injury would be more pertinent. If the privately purchased boots worn met BS EN345 and/or 347, then it shouldnt be an issue (for a competent injuries lawyer!)
You must wear issued boots during training, but on Final Ex you might be able to wear your own (Depends on your Pl. Sgt). In my battalion, you can only wear gucci boots out in the field... Otherwise its issue tissue all the way!
You would probably get away with wearing ProBoots in training.
Two guys i did basic with took their own boots. One had been TA, the other ACF instructor so they were Issue style boots anyway! No instructors said anything (poss cos they didn't notice).It certainly helped their turnaround speeds before lessons after a tab! (Boots already clean and polished)
Of the two pairs of boots i was issued, I broke both pairs in then used the most comfortable for working and the other pair for best. HANDY HINT- Before you start to bull your best boots. (2nd least comfortable pair) Keep them polished and clean at all times. This means that should you get show parade you have a nice clean pair of non-scuffed boots to use!