I've just got WinMo booting from u-boot. Actually, not directly, I've got WinMo bootloader booting from u-boot, but that's enought to get WinMo booting :)
It means that we can get dualbooting on h1940 and rx1950. Neat :)
Some technical details:
WinMo bootloader location in nand is 0x4000-0x44000 (for h1940 and rx1950), so backup this area to be able restore it/or boot it from u-boot.. Its load address is 0x30080000, it expects interrupts, mmu and dcache to be disabled, doesn't care about icache. Entry point is 0x30080000.