Helen Clark has made her "big" housing announcement, and its... allowing people to build houses on crown land. If this looks awfully familiar, its because National proposed it in September (though with the ability to buy the land, which makes it a more attractive policy). So, not only is it not a gazump, it's not even new.
OTOH, maybe Labour is just returning the favour after National reannounced Michael Cullen's policy to shift New Zealand Superannuation Fund and KiwiSaver investment back to New Zealand. Though in National's case, they would also shrink that pool of investment by cutting KiwiSaver, which is just a bit contradictory.