Would the polish tax office also want to tax any interest he earns in his Aus savings account if he is in Polska >185 days per tax year? Or is there some treaty agreement meaning it's not taxable? I think I'm right in saying Polska is less generous with personal tax allowances.
They certainly would be very interested, and if his lifestyle in Poland suggests that he isn't declaring the right amount of tax, they'll go ahead and make a few assumptions.
I would prefer to remain Australian for taxation, in fact. Work doesn't even have to know where I am.
You might prefer, but the Polish taxman will insist, and he's not a generous lover.