We could confidently expect a terse statement along the following lines:
As Mr McBride no longer works for the government, the Conservative Party fully accepts that Gordon Brown and the Labour party can't reasonably be expected to comment and as far as we are concerned that's the end of the matter.
How could I be so sure? Well, when former Conservative candidate for Watford Ian Oakley was convicted for spreading anonymous smears against political opponents (of a rather worse nature than those in the McBride-Draper email), and mounting a sustained campaign of harrassment and criminal damage against them, the Conservatives were reported as saying the following:
A spokesman for the Conservatives said they could not comment on the issue as Oakley was no longer a member of the party.
It is rather odd, therefore, that the BBC website reports Cameron as being 'furious' and calling on Gordon Brown to 'give a guarantee that such messages will not be sent again'. Meanwhile William Hague has 'demanded an apology from the prime minister'. It seems that the official Conservative view about smearing political opponents has temporarily slipped their memories and perhaps the Conservative Central Office aparatchik who released the statement on Oakley should remind them.
By any standards, however repellent McBride's behaviour may be, it pales into insignificance when compared to Oakley's. Unlike Oakley, McBride did not personally make his poisonous material public, he has offered some kind of public statement of regret, and a Labour cabinet minister has repudiated his behaviour (albeit with in my view quite a bit of dissembling).
In contrast, none of Oakley's erstwhile colleages in Watford Conservatives have expressed regret for his behaviour. Cameron now has apologised, but not until seven months after the conviction, and even then only after being directly asked by a member of the public in a way that meant he could hardly avoid doing so. And he certainly didn't offer a guarantee that it wouldn't happen again along the lines that he now demands of Gordon Brown.
Of course the BBC news report cited above probably doesn't quote the whole of the Conservative party's statement on this matter. Perhaps in full it reads:
The Conservative party are furious and believe that Gordon Brown should apologise for Mr McBride's behaviour, but we accept that first of all he should pretend it's nothing to do with him, that any apology should only be made after several months have gone by and even then issued only if the prime minister is put in a position by a member of the public where it would seem churlish and mean-spirited not to express regret.