I can confirm that the Dual XGPS150A can connect to a Surface RT running Win 8.1. However the results may not be what you want. I bought the BT GPS receiver about a year ago so that I could add GPS to my iPad2. The iPad pairs up perfectly and the iOS location services automatically sense the GPS signal. There are a myriad of mapping an navigation apps that make use of offline maps that I have used for driving, boating, etc. The iPad works great, the Surface RT not so much.
Here is what happens so far. The instructions quoted above work as advertised on the Surface RT and were really easy to follow. Just pair the BT device and the Surface automatically picks up the receiver. The only weird thing was that the GPS was initial sensed as "Other" device but the instructions covered that. Win 8.1 even auto-configured the COM port so I did not have to follow the second half of the instructions!
Now the bad news. Despite being paired, the GPS will not connect. I am told that the connection will not be established until an app on the device calls for GPS data. I am unable to find an app that does this. There are several mapping apps and even some GPS apps but each seems to call the Surface RT location service which is pulling its location data from the WiFi connection and not the COM port. When I turn off the wireless, all apps loose their location data despite the paired BT GPS device being on and available.
So far I have been unable to find a way to configure Surface RT's location service to pull its data from the BT GPS instead of the WiFi, but I have only been at it for a few hours. I may find a solution yet and will post it if I do. Or if someone else know how to do this, please share.