Is it permissible to work in repairing refrigerators in restaurants that contain pork alongside other foods, and is the wage earned from this work lawful or unlawful?

The basic principle is that it is permissible to interact with a non-Muslim in buying and selling and leasing, unless it is known that what is being dealt with will be used exclusively for unlawful purposes. This is supported by the permissibility of leasing a house to a non-Muslim for dwelling, even with the knowledge that he will commit unlawful acts therein.