Low bottom brackets are associated with more upright seating, but they don't have the exclusive. Having an upright seat and a high bottom bracket results in a closed hip angle, which doesn't suit some people, but others claim lets them produce more power. Lightnings are pretty upright and have high bottom brackets.
Older RANS models are upright enough to count, too -- Rocket, V-Rex have 'neutral' bottom bracket height (about equal with seat) and their older models of LWB such as Stratus are fairly upright but with lower bottom brackets.