From looking at the photos it appears to have a small area of slanted of ceiling and that the bottom cord is not resting on the wall? I think you are stuck if this is the case as you can not transfer the weight to the wall directly and the truss was not made to carry the laod you are planning. If I'm looking at the photo wrong please say so, other wise do not try this at all.
I see it the same way. The trusses in the existing garage have a slant to come up to the i-beam level. After that they weight is spread across the other webbing sections.
The other garage doesn't show an inside picture, but it appears they have a 2x10 (or 2x12) lvl as floor joist then they connect to trusses that have flat 2x8s on the rest of the way out. It's hard to tell if that is the header or all floor joists, I'm guessing it is all of them.
For the original poster, he would probably have to tear off the entire roof to do that safely the way his was built.
Those are 2x10 Boise Versa-Lam Engineered Trusses for the Floor from what I can tell in http://home-and-garden.webshots.com/...56333749HBpnUh with 2x6 on the right side to spread the load. I would not doubt that these where made for the project to begin with, not something off the shelf.
Yes for the floor truss are good but the ones in the garage area have a small area of cathedraled ceiling for the bottom 2' and that is not made to hold the added load and will not be beefed up in any way.