It has taken a while, but it is now happening.
A few months back it was reported that British atheists were being asked to contribute to an advertising campaign to counter christian advertising on London buses, but only a fraction of the money had been raised. The ads were to say: 'There's probably no God. Now stop worrying and get on with your life.'
More recently it has been reported that Richard Dawkins has offered a significant amount of money, matching whatever is given by others, to begin the campaign.
This was discussed by comedians on Sydney afternoon radio last Friday, and a couple of comments suggested the advertising might be underwhelming:
"If they were really serious, the ads would say: 'There's probably no God - sin away!'"
"Imagine if the ads said: 'There's probably not a bomb on this bus, so get on board.' Would you?"