A family member didn't pay for a while. He had to pay up for the entire duration eventually, even if he had switched providers. So I'd expect that insurance would have gotten the bill in case emergency aid would have become necessary. That's very different from the US, where you would have to pay the bill yourself (from my understanding).
In Poland, if you don't pay, then in theory the hospital bill comes to you (as otherwise, there would be no penalty for not paying). In reality, 99.9% is insured one way or another and it's really hard to find someone who actually did not pay the insurance and needed serious/expensive medical help to see what actually happened in his/her case - I've never heard of anyone like that. Also, our consitution says that "the authorities provide equal access to publicly funded medical care, regardless of one's financial situation". Which IMO makes the whole system unconstitutional, but no one bothered to challenge it yet.
In the US, hospitals are required to provide emergency treatment. When I was uninsured and needed emergency treatment about 14 years ago (before the ACA/Obamacare), the hospital made an attempt to help me apply for public assistance (Medicaid), because they assumed I would not be able to pay. I ultimately paid the bill in full, out of a (perhaps misguided) sense that I should because I could, but I was told at some point that they normally wrote off half of any bill not covered by insurance.
What happens if he can't afford that? Will they garnish his wages?