Apparently sun gate alignment was a recurring theme in Roman architecture.
Implications abound: A covenant situated on Roman ruins might get Ignem vis this way; an alignment could be an open gate day for a regio; there might be all sorts of sun god cultic artifacts entombed in a shrine or temple; this alignment might be well known and converted to a church; some faeries might be extra active.
As an aside, Roman settlements are pretty much always in a grid with a north/south and east/west axis. http://en.wikipedia.org/wiki/Cardo. Despite what the article says, looking at the geography of this fort's location it seems much more likely that in reality this fort was built askew to the normal orientation merely for the practical reason so that it would fit on the flat bit on top of the escarpment it is built on.
Having been to Hardknott a couple of times (and climbed the hill of the same name) I suggest that the alignment could at least in part be to best make use of the flat ground which is limited in this particular location. Also, the fort looks down Eskdale and lines of sight might also have been important in choosing the location. Thirdly, thee sun would be hidden behind various fells when it rose and set at any time of year so unless looked at with the third dimension in mind, which the article does not appear to account for, the theory would not be tenable.
Hardknott is a fair few miles south of the Wall.
None of this should detract from any Mythic European usage.