The problem is that WINE is not an emulator (as evidenced by the name), but an interface translation layer. Although the source code is available, and it's reasonable to expect that you could compile it (probably with some tweaking) to get it to run on the Power architecture, you are talking about fundamentally different instruction sets. Since WINE doesn't translate the raw CPU instructions but only the calls to the Windows APIs, and since Windows programs are written for x86 or x86_64, even having WINE running on a Power distro wouldn't magically get the Windows applications running. The Windows apps themselves would ALSO have to be written for the Power architecture.
CPU emulation has been done in the past (and indeed still is), but is usually so processor intensive that you typically lose several orders of magnitude in performance (this varies somewhat depending on the disparity of the architecture doing the emulation vs. the architecture being emulated as well as the quality of the emulator itself, but is generally true). As a consequence, it's usually only practical to emulate relatively old and slow CPUs, even on modern hardware, at least if you are looking to emulate full performance of the original CPU.
