There shouldn't be any problem with this whatsoever as long as it's a universal policy. Police have enough problems with 'respect' as it is, the G20 being an example thereof. I think it's a positive thing that they want to try and become more 'approachable' to the general public (ie. everyone who resides in our fine country).
The only negative things connected with this general topic have nothing to do with the head scarves. I am more concerned about having a religious court system which works outside of our own justice system than someone having to cover their hair temporarily on the rare occasion that they are required to enter this particular type of place of worship. It's not like they are going to make non muslim police officers to wear an head scarf and watch over the services held in a mosque at every possible occasion.
I'd be more shocked if they decided to implement police presence in places of worship in general because that is wrong.
The example of France that is often cited is, don't forget, for all religious garb that is on show (so a necklace with a star or a crucifix on it which is concealed, thus not in view of others is ok) being banned in schools. Their example is for everyone and is not selective.
In a way I think it's quite a nice thing to see a police officer wearing his turban whilst doing his job: keeping the peace. A happy officer is far more likely to do his job better. Plus in some communities people might be more willing to approach him. Maybe, just maybe, they are trying to bring back the old notion of the friendly neighbourhood Bobby who everyone knows, who stops and chats to residents and who makes everyone just feel that little bit more at ease.
The cold and intimidating image that many police give off (not all, mind) is only negative and will only fuel more people making outcries against our police force. Such as has been seen during the G20 manifestations.
It shouldn't be police vs people as is often portrayed by popular culture or by popular opinion. Look at any show which depicts riots. It's all about the "us vs the police". It just shouldn't be.
If it helps to make my community safer, then I'm all for it.