Pine tar is not considered to be a toxic substance per se. Too much pine tar, however, for too long could cause cancer. If it is layed on thick enough, it could block the pores of the cats skin and interfere with perspriation and cause the body to overheat.
You can remove pine tar from cat fur in the same way you would remove it from human hair. However, know that the process could strip the natural lubricants and oils from the cats fur and skin, temporarily. You will need to also obtain some products from the veternarian or pet store to treat the fur and skin when you are done with removing the pine tar.
DO NOT use solvents or gasoline. These products can be toxic and lethal to your pet.
The single best method is to cut the hair/fur off. THis will get rid of the majority of tar. You can get rid of the residual by soaking the cats fur in vegitable oil, and letting the remaining pine tar soften, then remove by shampooing.
Once done treat any remaining fur and the cats skin with lotions and ointments from the vet or pet store.