"Legal'? A medical license legally allows you to do whatever you want, both in medicine and surgery. So a licensed FM doc can legally do a CAGB, and a CT surgeon could open a primary care clinic and manage diabetes and hypertension all day long.
But yes, cardiologists to PTCA all the time. I know in theory CT surgeons can do them as well, but I've only seen cardiologists do angiograms and coronary angioplasty. And to be a cardiologist you need to go through IM first, so you really don't have to specify "IM Cardiologist."