The general standard of cycling among Cambridge police is pretty low.
Generally they're hugging the gutter or, at least, not even in a good secondary position. Most of them are very slow, tentative, timid even on the road. They're not trained to behave like good cyclists, and the biggest surprise for me with this story is not that the police officer had no lights, but that she was out on the bicycle after dark.
And I'm afraid that attitude carries over to how cycling is policed in Cambridge. Fair enough, get caught out without lights, you should be stopped and advised or fined. But staking a street out for days on end and stopping cyclists? The expense of doing so is not justified based on the benefit it can bring. To see Plod stop a cyclist at a junction for having no lights while allowing cars to go through the red light... I dunno, seems to me that the cyclist cops it for being an easier target.
Then theres are narrow sections of path between two cyclable roads/cycle paths, which many cyclists tentatively and safely ride over. Fine, technically illegal, but there was a police officer (two much of the time) stationed every day on one section (next to the Town Hall, Market Square) for days earlier in the year; it didn't do any good, it didn't make things safer.
Go to Cambridge plod with video footage and eyewitness accounts of dangerous driving and they do nothing. Literally, they'll say 'oh well the CPS don't care about these things, theres nothing we can do' and thats it.
The reality is that Cambridge Constabulary see cycling as a means of getting good publicity; 'look how many cyclists we've stopped riding irresponsibly', 'look at out PCSOs riding around'... But when it comes down to it I have seen no evidence of them being in any way skilled in cycle safety, or at any time able to give cycling offenses the kind of priority that is important.