I found that often the company knows the binding site but are not keen to share the information. However, if a company sells both clones they might be able to tell you at least whether the binding sites are the same/different.
Unfortunately, Pieter is exactly right. This is especially true with Abs that may be of current special interest for commercial pharma, immunotherapy, etc., like anti-PD-1. Also, many suppliers don't actually know the epitope or immunogen, because they are not actually the manufacturer of the Abs and the originator does not provide them this "sensitive" data.
I deeply depreciate your input. I actually had a little time to test it. I stained few cells with EH12.2H7 in one color, washed and stained with EH12.1 in another color. Apparently the prior staining with the first did not abrogate the binding of the second so i believe they do not share the same site.