They look like they're based on standard 25mm rounds, like many of the HF catalog photos are, eg:
Should be able to compare them based on that. Seem pretty similar to me, and of course heights vary a lot in real people.
Yeah, it's more a question of dimensions/style - the things that set minis apart as not quite 'in scale' are especially heads and hands.
Not that I normally give a damn - I mix and match Hasslefree, Red Box, and Heresy freely, anyway, and as these sculpts seem delicate enough, I'd probably be fine.