News of the Polish Leopard 2s going to Ukraine is not breaking new. But there are some more details.
Only 12 Leopards? I don't know what 12 Leopards can do for Ukraine at this point. They need hundreds of new MBTs.
Looking at the Polish pattern of sending their troops into Ukraine and then rebadging them as Ukrainian troops. speculate that these Polish Leopards will be manned by Polish crews. Probably an entire Polish tank company, rebadged as Ukrainian. No Ukrainians are gonna trained fast enough to crew them and fight now.
It'll be good battle experience for the Polish tank forces, even if they get killed. But for the Russians, it'll be a priceless opportunity to fight against a defacto company of NATO Leopard 2s. Even better if they could capture some intact units.