"Fort William is good at football now."
Translation:Tha an Gearasdan math air ball-coise a-nis.
That's exactly what it translates to and yes, there was a fort there. The town really should be renamed considering it's named after Butcher Cumberland and the fort was an English attempt at controlling the Highlanders...but beyond the historical significance of the name, that conversation is a bit outside the scope of the forums.
Generally, teams are referred to in the plural in the UK, but as has been pointed out where, it is grammatically correct to use the singular, so either is acceptable in the UK and I think it comes down to what the person writing each phrase perfers. I, personally, would interpret Fort William is good at football to mean that the town of Fort William produces good football players, whereas Fort William are good at football to mean the team called Fort William is/are good at football.
Judging from other comments, using the plural would be considered unacceptable in the US.