No. Linux cannot run either Logic nor Cubase. Both are very intricate programs that have very high demands on both software and hardware (ASIO drivers, etc) so running them under quasi-emulation (using Wine for instance) does not work.
I run a little recording studio along with a couple of friends. We have resorted to using Windows 2000 since we already have a Logic license, and quite frankly the Linux projects aren't mature enough just yet. The foundation for good audio software has already been laid with the preemptible kernel (standard in Linux 2.6), lowlatency patches and most of all the Alsa sound architecture. Add stuff like the lowlatency soundserver
Jack and a harddisk recording environment like
Ardour and the future starts looking quite bright.
I have tried Ardour a couple of times but it cannot really compete with Logic just yet. But don't be scared of the Mac costing money - you're still going to spend a whole lot of cash (traditional mics, condenser mics, a good mixer, a multichannel soundcard and so on). If you want a really good soundcard for the money look at the STAudio
DSP2000 C-PORT. Excellent value and it blows all products in the same price range out of the water.
Håkan