That line about wherever else nearby you may be just seems to me like an catch all for your offsite hotel, breakfast, your house, whatever. That would be big yikes if they attempted anything more complicated than allowing a park reservation holder to book a BG, IMO. I do not trust their systems to do that.
You should theoretically be able to book a BG from Canada (hi

) if you have a reservation attached to you, just like I could get a BG from here if I was logged into someone’s account who was in DHS.