It’s happening to me right now. The show, a carbon copy of my idea even the exact title, is going to air on the 24th on a cable network. I ‘protected’ the idea, so I thought through WGA but it seems that ideas can’t really be protected and you have to find the person who stole the idea to get the smoking gun. There is a lot of turn over in these companies and anyone can take your idea someplace else after it was rejected in the Producer’s Portal.
If you make a pilot of the series, then you are more protected. I also recommend copyright. Best is to have representation – that’s the only way.