Many devices/platforms are supported by Microsoft. The Banana Pi isn't listed here. But the specifications of the Banana Pi (first generation in this case) are quite similar to that of Raspbian Pi:
╔═════╦═════════════════════════════╦════════════════════════════════╗
║ ║ Raspberry Pi 2 B ║ Banana Pi (1) ║
╠═════╬═════════════════════════════╬════════════════════════════════╣
║ SOC ║ Broadcom BCM2836 ║ Allwinner A20 ║
║ CPU ║ ARM Cortex-A7 1GHz Dualcore ║ ARM Cortex-A7 900 MHz Quadcore ║
║ GPU ║ Broadcom VideoCore IV ║ Mali400MP2 GPU ║
║ RAM ║ 1024 DDR2 RAM ║ 1024 DDR3 RAM ║
║ LAN ║ 10/100-MBit-Ethernet ║ 10/100/1000-Mbit/s-Ethernet ║
╚═════╩═════════════════════════════╩════════════════════════════════╝
Source: http://jankarres.de/2015/03/raspberry-pi-2-performance-vergleich-und-benchmarks/
My Question: Is is possible to get Windows 10 IoT running on a Banana Pi (not only theoretically)?
It is now possible (officially) to run Windows 10 IoT Core on the newer Banana Pi (Allwinner Technology Banana Pi BPI-M64, Allwinner Technology Pine64) Boards:
And maybe useful for a custom try: https://msdn.microsoft.com/en-us/library/windows/hardware/dn916104%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396