I get the impression that the lowest common denominator of Oblivion's performance comes from the speed that it can get data from the DVD, since the HDD does not seem to have significant impact outside of caching assets. In which case, it's probably worth finding out how well Game Bryo works with redundant data to minimise seeks.
People keep mentioning that the size of Oblivion on the 360 is the same if not a tiny bit more than the PC install, which suggests there is little to no redundancy on the disc itself. If that is the case, then I think a lot of what is holding up load speeds on 360 (and probably the stuttering that occasionally happens) is the additional seeks. A lot of that potential throughput from the 12x DVD drive is lost when excess seeks are made thanks to a dataset compacted for minimal storage usage rather than streaming efficiency.
I'm not saying it would work miracles, since the PS3's drive does still have a lower throughput and significantly slower seek times than the 360's, but it should go some way to help with load times. It should also help in making the game world smoother as textures are streamed off the disc without too much seeking. I think that just transposing the assets as they are existingly packaged would have definitely proved untenable for the PS3 given its drive performance, so there has to be reliance on redundancy in my opinion.
I'm going to be really non-committal here though, since it depends on too many factors like the developer talent, port budget, engine suitability, and the way that the game was designed in the first place. I would at least hope they are addressing the issues that a slower performing BD-ROM drive poses.
