The bubonic plague did work for the mongols. Killing 1/3 of the population of europe. If ISIS use ebola as a weapon I don't think this will not work for them. Ebola just infected an american nurse in dallas without the terrorist help how much more if the terrorists is added to the equation.
Probably trying to spread ebola wouldn't be a great success. How these infected terrorist can inject their bodily fluids into many people without being noticed? Sneezing and coughing on crowded buses or trains? Yes that could do some harm but I think they would be more effective with a few dozens of traditional hand grenades.
Hm. Actually, you might be on to something. If the martyr were to explode himself from the inside with grenades, there'd be ebola-carrying gore splattered everywhere. What if he goes to a concert (ehhh... one of those mosh pits or whatever they're called, where they all stand around each other) and blows himself up? It could spark a pandemic. I doubt any first responders would think to check if the guy who blew himself up was infected with ebola, so you could have hundreds of people going about their daily routine for maybe 2-4 days before there's a massive round-up.
ETA: Okay. -So you have two guys go in, at least one infected with ebola. The first guy gets tossed up into the air by the second guy - or maybe only one guy who uses a trampoline - and they try to time it where the guy explodes when he's fairly high up. I'm not sure how far out his parts or blood would go, but I'd guess there'd be a way to get a majority.
Your scenario would probably not work. First of all, these raves generally have some level of security so I think it would be unlikely that someone would be able to get grenades inside. Assuming they were able to do so, I think that blowing themselves up would likely kill most of the people who would potentially get infected. Additionally the only way to contract ebola is to mix someone elses bodily fluids with your own so the person who is infected would need to get their blood into other people's eyes or into an open wound.
Lastly, I don't believe that everyone who comes into contact with ebola will actually contract it (I may be incorrect on this). It will not be possible to know for sure if someone has ebola until either the incubation period has expired or they start to show symptoms, so a terrorist would not necessarily be able to infect someone until the person has symptoms and by then it would be obvious they are sick and would be quaranteened