I asked for my SIP URIs to be included in the TPS...
The first time I got a response of "we can't but we'll ask OFCOM", and OFCOM answered very much "TPS can only do digits".
But to my surprise, having written again (from work this time) I actually got a more comprehensive reply. This may be because I complained to the ICO, not sure.
Basically he is saying the definition of "Number" (as in "Telephone number") in the Communications Act 2003 is not carried across to the Privacy and Electronic Communications (EC Directive) Regulations 2003. So they only accept "numbers" in the traditional sense.
I may write back, as, indeed, he is right, there is no definition of "number" in the PECR, so one would indeed expect it to be "number" in the traditional sense... But "registration number", "vehicle identification number", "national insurance number", "serial number", all of which allow things other than just digits, so there is not really much "tradition" in numbers only being digits, certainly not in law.
It also seems to me that the TPS has to list numbers "allocated to a line", and "line" covers things that perform the function of a line. My SIP phone here clearly does that and the "number" allocated by my telco to that line is my SIP URI - i.e. it is my telco that has allocated the SIP URI as a "number", so it counts.
He does say that he will ensure the proper regulatory treatment of SIP addresses is brought to the attention of the relevant authorities in the future. It seems mean having a go now - as he has tried, but I'll give it a go anyway...
Update: I have replied to him :-
Update: The TPS site won't accept my Iridium mobile number, so I am writing to them to add that. That is only digits, so they should accept it. Of course, I know that no junk caller would be mad enough to ever call it, but I am entitled to have it included in the register I believe.