Yes, that is certainly a real phenomenon. I was speaking about 'discrimination' in it's wider sense, however, as in that there are clear rules about a cabbie's

Yes, that is certainly a real phenomenon. I was speaking about 'discrimination' in it's wider sense, however, as in that there are clear rules about a cabbie's ability to reject a hail based on certain factors (like distance/time, but also race). In reality this does happen. I've frequently been refused during 'feeding frenzies' at my local train station based on the fact that I'm not a tourist (and thus know the rules), my trip is too short, etc. In theory by rejecting a legitimate fare a cabbie is risking more than a scab would be risking (historically). Under an Uber/Lyft/etc system this problem is mitigated, probably even better than the medallion system.