I just don't believe it. I find it hard to believe any politician these days, he's clearly trying to find a popular policy idea that will get him votes. When actually in power, no doubt this will slide onto the back burner, or it will be announced that because of XYZ issue left behind by the Conservatives, that it's no longer possible. Or similar.
And of course, if prison estate becomes essentially mixed sex/male instead of female/male, then there's one set of vulnerable women who won't be seeing an improvement in their circumstances.