OK, there is a rule (general condition 4) that says we have to make location data available to emergency services for 999 calls (and 112).
My reading of it is pretty simple in that (a) there is no location data in the signalling system, so nothing to send, and (b) we only have to make available which could be a web site if we wanted - nothing requires us to even "agree technical standards".
OFCOMs view is very different, though they fail to explain why in any sensible detail. They consider we have to update BT's database for emergency calls (based on CLI). Well, we could use C&W database and routing instead, they say. But still, we are expected to send (not "make available") the data in a specific way to a specific system.
Lets try and meet that new and unwritten requirement shall we?
Catch is that for a load of the numbers we have we can't do that. The issue is we have two carriers and number hosters and a load of numbers actually from one of the carriers. We only use one carrier for 999 calls. We can only update the numbers we have hosted with them on to BT's database (for now). So a whole load of number we cannot yet update. We have around 4 million numbers we can and a few thousand we cannot.
There is a long term plan (which could be months to sort this) allowing us to update for any of our numbers via the one carrier. However OFCOM are bullying. No amount of "we do actually comply anyway so stop bullying" is working.
So I had a cunning plan. A simple plan. It is a sort of NAT for phone numbers (someone on irc suggested it was Customer user Number Translation or CNT for short). But basically any numbers I cannot update gets an 0200 number allocated and that is updated in the BT database. Calls to 999 present the 0200 number, and they get the location data. (0200 is a special code for hidden numbers in the network, so ideal for this).
Job done - compliant - all end users calling 999 can have location data (if they set it).
Is that good enough for OFCOM?
No, of course not. But I cannot see how it is not compliant. They seem happy with it as a temporary solution. It makes no sense - either it is compliant or it is not. There is no "temporary" to it!
We will have to see what they say.