Exactly as
@Box Brownie says, knock for knock used to be where there was no obvious side on whom to put the whole blame. now it's a case of whatever is cheaper for the insurance company, but customer NCB plays no part in the cost calculation as far as that's concerned.
Purely FWIW
I have in a sense a vested interest as follows:-
I had a bump earlier last year ~ this was a situation of me and the other party reversing into each other in a small local shop car park.
All reported AOK to insurers and mine said "is there CCTV to show how you and the other party were moving...." I asked at the shop and there was but DP protocols meant that I had to apply to the HQ of the company this I duly did within approx10 days of the incident. The form allows the shop HQ 40 days to check the records and reply............................fast forward to day 41 and I get a letter to tell me that my request could not be met because the time had elapsed and the recording was no longer available. I took issue with them about when they got my request and how long they had taken meaning it had expired!!!
NB when I initially spoke to my insurer the contact said please be aware that the CCTV may show that you were the "at fault party...." I told he I fully accept that if that was proved!
In about October last year I asked my insurer whether it was all resolved? They said the third party's insurer was being non responsive to their communications
and to ask them again in a couple of months. Well, life goes and I forgot about it (please bear in mind both vehicles had been repaired long ago)......in Jan this year I phoned for an update and was told the third party insurer was not replying to my insurers submission that the matter be closed with a knock for knock agreement (Note~ if this is agreed I would get 50% of my excess re-paid).
In this non communicative situation, which I gather is non uncommon with that other insurer, they take the step of passing the case to their solicitors and I have with no financial risk [I have this in writing] I sign off on them taking court action against the 3rd party. I sent forms back and have yet to hear anything further..................it sounds to me like this has become an impasse but find it odd that on the face of it it is, it appears, an unresolved case??? I will phone my insurer sometime and see if they have any update???
PS again for the record there was no definitive CCTV evidence to show who was to blame to a 50/50 IMO would be the most logical outcome.