If they succeed in selling DBCT, it may be irrelevant in any...

If they succeed in selling DBCT, it may be irrelevant in any case what the ATO decides (apart from potential penalty fees if it goes in the ATO's favour).

If the expenses were not deductible in the years they were incurred, they will be added to the cost base of DBCT and reduce the capital gains tax that will be owing on profit from the sale.

I may be wrong, but apart from penalties imposed, the net effect will be the same with regards to the tax liability.