Considering that WOA will not be sold separately and how MS touts tight integration with hardware, I'd be willing to make a bet that consumers won't be able to buy an ARM device with WOA that can boot to Linux (without exploits).
"Partners will provide WOA PCs as integrated, end-to-end products that include hardware, firmware, and Windows on ARM software. Windows on ARM software will not be sold or distributed independent of a new WOA PC, just as you would expect from a consumer electronics device that relies on unique and integrated pairings of hardware and software"
http://blogs.msdn.com/b/b8/archive/2012/02/09/building-windo...
"Partners will provide WOA PCs as integrated, end-to-end products that include hardware, firmware, and Windows on ARM software. Windows on ARM software will not be sold or distributed independent of a new WOA PC, just as you would expect from a consumer electronics device that relies on unique and integrated pairings of hardware and software"