I believe they can. The only case I have seen where this happened, the Bankruptcy Court Judge/Central District, tossed the request out because the 2nd mortgage had not been perfected. (late filing I think). Note that the judge did not choose to take the simpler course which would have been to disallow the petition. I am led to believe the IBP was spot on.
With such a large set of , overvalued real estate, now upside-downed, 1-2 new home mortgage purchases, bankruptcy lawyers, adversarial and defending, should be having several field years, er days, er years.