Exactly. If they are in the same universe there's no logic to the story line. It wasn't a matter of wanting the Doctor to show up as much as there was no reason he couldn't.

And mind you, it's established in "Journey's End" that Tosh is a master at planning for unexpected things, which makes the whole plot from day one onward make no sense. If she prepared something for a Dalek invasion she'd surely have come up with something for explosives in the Hub.