Looking at the thinking behind it, the intention is not to change the revenue model (petrol prices would not be slashed although duty and road tax would be reduced) but primarily to reduce congestion.
As most musical events occur outside peak hours, I don't imagine it will impinge on the average enthusiast greatly.
There is some information on the scheme here.
The scheme as envisaged tracks the car - not you. Unless you are under direct observation no-one knows who's driving the car. (Your movements are monitored by the rdf tag secretly implanted on you last time you visited the dentist!). If you honestly think that there is a civil servant given over to watching you, you have an over inflated sense of self importance. Got a mobile phone in your pocket? "Big Brother" knows where you are every minute it's switched on.
As for the efficacy of such a petition, there are more than 2000 of them on the site, ranging from the sensible to the totally barking and the national to the very, very parochial. They are hosted on the No10 site, but they are organised by an outside organisation called mySociety. As such they have no 'official' standing.