Re: What database?
The only way a filter can work is if there is a central government database. To use your copy of the government example: to find the owners of phones near to where three crimes were committed, requires that the data is on a common database since there is no way that EE can know that person A carrying phone X is, or is not, person A carrying phone Y on the Vodaphone network. Very few crims (unless they sit in Westminster) are stupid enough to carry the same phone to different jobs. Ergo, the common database must be held by the government (or a government appointed authority) since it would be illegal for anyone else to do so.
What they continually gloss over though is the fact that anyone can buy a cheap phone without any identity check and pop in a prepaid sim card, then throw it away once the job is one. Which gets us back to the real reason for this bill: to be able to retroactively go though the masses of data in order fit up any innocent person and so improve the crime statistics.
As they say, if you have nothing to hide, you have nothing to fear (except abuse of due process).