Toast 8's Blu-ray support is strictly data-only. If you had a Blu-ray folder structure pre-made by other authoring software, Toast could burn it for you... but there's no Mac software to author Blu-ray yet. (Of course, since you have a Mac Pro, you could always run Windows software for Blu-ray creation using Boot Camp. I believe Roxio has another product, DVDit Pro HD which can author Blu-ray under Windows, and there may be others.)
The other problem (once you do get a Blu-ray movie burned) is finding a Blu-ray player it will actually play on. There are two different types of Blu-ray video disc: BDAV and BDMV. Only BDMV supports the full Blu-ray feature set, and most players will refuse to play BDMV from a BD-R recordable disc. The PS3 is the largest-selling Blu-ray device so far, and it doesn't support this (even with the newest firmware). Even worse, the manual for Sony's brand new BDP-S300 set-top player lists BD-R and BD-RE under "Examples of discs that the player cannot play," so I don't think this is an issue they're worried about fixing any time soon.
Personally, I've just given up on Blu-ray video authoring, and use my Blu-ray burner for data archiving (because of the compatibility issues, plus the fact that my Macs are all PPC which precludes using any Windows authoring software). If I need to get HD video on a disc, DVD Studio Pro lets me burn a basic HD DVD onto DVD-R, and the Toshiba HD-A2 will play it without complaint (Apple improved this compatibility in 4.1.2). Hopefully the next version of DVDSP will magically sprout Blu-ray authoring support, but even if it does Sony et. al. may not have sorted out the player issues by then.
-Frank
