Legally, I'm pretty sure that the WA cannot become law unless the HoC vote for it.
With all due respect, that's assuming that any attempt the the government - ultimately Theresa May - to continued as if had been passed without it passing can actually be stopped.
The UK doesn't have such a clearly defined separation of powers that attempts by the government to act ultra vires are bound to fail. There's no automatic mechanism to ensure that.
So, let's play Brexit blue-sky, and try and answer the question:
What if Theresa May decides to act as if she had succeeded getting the WA through parliament, even though she hadn't ?
Will the civil service refuse to carry out it's provisions ? Will each government department refuse to act ?
I'm afraid I have zero faith in those last two.
Will the police (the paramilitary wing of the Home Office) refuse to arrest people for not carrying out the WA provisions ?
(Anyone seen a court room yet ? I haven't).
Carl Sagan once said (or has been [mis]quoted as saying) Extraordinary claims, require extraordinary evidence ... by the same token, Extraordinary events require extraordinary thinking (© D.G. Rossetti, 2019). I think it's only now that some commentators are starting to realise "somethings up".
I'm trying very, very hard, because ultimately it was impossible for them to have known, and (unlike moron, cretin, brain-dead, Brexiteers) I am quite willing to admit that at the time I poo-poohed the warnings. But it's possible to blame a lot of this on the LibDems and the Fucked-Term-Parliament-Act. Because without that, we would have had a GE by now. But we were warned. We (well I) ignored those warnings. If the current state of affairs is in part due to that, then I accept my share of the blame.
(This is not to say I don't think we shouldn't have FTPs. But maybe we rushed into it
).
Over to you 