Praise be to Allah.
We put this question to Shaykh Muhammad ibn Saalih al-‘Uthaymeen, may Allaah preserve him, who answered as follows:
If you buy the tins, then it is not permissible, because it is not permissible to pay for pork and buy it. But if a person finds it by chance and feeds it to his cat, then there is nothing wrong with that.
And Allah knows best.