From what I've been able to piece together, this building was originally constructed as a dedicated observatory for the Canadian Astronomical Research Group in 1976. The equipment, apparently including a 24" telescope, was removed in 1997, and the building converted into a private home.
Source: Journal of the Royal Astronomical Society of Canada Newsletter, Vol. 71, p.L7
UPDATE: This location was demolished sometime between this visit and June, 2013.
Imagine having a house with a two-car garage, 2 bedrooms plus a master bedroom, a jacuzzi tub with heat lamp, large dining room, large living room with hardwood floors and a commanding view from a hilltop. Now, imagine that you can walk up a curving staircase to your own observatory dome.
For some reason, these people had that and walked away...