Microsoft probably has exclusive rights to the first title in the series being the titles publisher. I suspect that Microsoft allowed Electronic Arts to have the PC publishing rights which were probably reserved for Microsoft as part of a licensing agreement for the remaining two titles in the trilogy.
Despite claims to the contrary Electronic Arts does have platform specific studios, and if the title will see a near simultaneous release on both the 360 and the PC there is probably very little motivation for a PS3 port. Given that most PS3 owners probably have access to a PC that could handle the title, and the fact that the console will probably never see the first installment in the series it seems like a near impossibility.
So in response to the question probably no on the PS3 port of the first title, and probably at the very best a timed exclusivity for the remaining two titles on the 360. However that will probably not be too pragmatic for interested gamers if the PC release is simultaneous or near to simultaneous.
We have to remember that Nintendo published Banjo Kazooie in 1998, and the year now is 2008. The title is making it to the arcade ten years after it originally arrived on the N64. Which in my humble opinion means one thing, and one thing only. Nintendo has had its publishing rights lapse. Publishing right do not last into perpetuity. They last for a specific time interval. In this case Nintendo probably retains publishing rights for ten years. So as time goes by publishing rights for Rare games will revert back to Rare and thus to Microsoft.