Terrorists are not going to be able to achieve respiratory transmission. What they can do is spray it in small droplets which is obviously bad enough. In that study the animal's cages were 20 cm apart. Apparently in the book Hot Zone which I haven't read, it spread room to room, but that's not what the study says: http://www.nature.com/srep/2012/121115/srep00811/full/srep00811.html?message-global=remove&goback=.gde_4429892_member_187356406
They can smear it on public door knobs, bus seats, toilet seats, etc. They can get jobs in eateries and put it in the food. Lots of ways for them to spread it.
qaStaHvIS wa' ram loSSaD Hugh SIjlaH qetbogh loD! (Four thousand throats may be cut in one night by a running man -- Klingon proverb)