1080i is actually what a majority of TV networks broadcast in, (that ore 720 60fps), but that's not to say that they material doesn't original as a different format.
1080i is tricky to work with in post. but on a good note, the files are half the size of 60p video, but still contain the temporal motion of 60fps. (geek talk)
but if you have video apps like After Effects or Premiere, you can use them to convert 1080i to ok looking 720p (60fps).
But unless you specifically want to slow down your Vision video, you're probably best just sticking with 1080 at 30fps (if it can do it)