I am pretty sure that this number is wrong. 3 years ago I heard from a reliable resource that it is about 30-40/y though that year was exceptionally low with only 15 or so graduates.
Just to get an idea look at the fellows in most programs. For example, I go to one of big California programs once a week to attend their conferences. They don't have any fellow in alternative pathway. I know that most or probably all Cali programs don't accept alternative pathway anymore. 10 years ago they used to have about 20% of their fellows in alternative pathway. Also consider that having a fellow who did not do residency in US does not necessary mean alternative pathway since there are some people esp from UK who come to US for a year of fellowship and then go back to their home country. It seems finding a radiology fellowship in UK is very hard.
Anyway, the alternative pathway is stupid and should be phased out.
To OP: Even if you can enter alternative pathway, you will have a very hard time getting certain fellowships in US. I assume it will be very very hard for a none US resident to get fellowships in IR, mammo and MSK while these fields have more US applicants than positions these days. Body, Chest and Nucs fellowships are still easy to get buy it seems they have enough US applicants.