The EU has a cap and trade system ("EU ETS") for large industrial installations. So as far as I understand, the Poland coal plants are not invisible to the EU. They pay a market price for each ton of CO2 emitted.
Poland does try to cancel out the price signal sent by the EU ETS with billions of subsidies. I guess that's part of the reason why they emit so much. But the emission cap still holds; if Poland pays for the right to emit a ton of CO2, then that ton cannot be emitted elsewhere in the EU.
https://www.europarl.europa.eu/news/en/headlines/society/201...
Poland does try to cancel out the price signal sent by the EU ETS with billions of subsidies. I guess that's part of the reason why they emit so much. But the emission cap still holds; if Poland pays for the right to emit a ton of CO2, then that ton cannot be emitted elsewhere in the EU.
https://ec.europa.eu/commission/presscorner/detail/es/ip_22_...