Rubadub, good question. Well, this law has actually been used and although it's been around for a while, many actually found out about it because of a family that faced social boycott from their community because of opposing virginity tests.
https://www.indiatoday.in/india/story/maharashtra-family-faces-social-boycott-for-opposing-virginity-test-1526253-2019-05-16
Being a black sheep is a whole different scenario. The social boycott law applies to when there is a formal announcement or resolution made to exclude a person from a community. So if the congregation was to announce that someone was no longer a JW and that led to shunning, or if there was no announcement but word got around and a person was shunned, or if there was a marking talk and a person was shunned. the congregation could be taken to court. The only proof that the courts require is that this is indeed shunning resulting from religious rules and there is ample evidence in the WT's videos and publications.
A lawyer I spoke to said that there have been numerous other cases filed (apart from the one in the link), but none have come to the attention of the media until now. It takes activism for the media to pick up a case, and I'm sure that if exJWs go to court, the media is going to gobble up the news. From the short while I've been in India I've learned that if you want courts to move fast and if you want a case resolved, take the media with you to the police station and have them follow your case. It's funny how fast people work when there's a journalist in the picture.