I love data-driven bug hunts like these and like the classic 500-mile email.
Especially when they're transit-related. I once spoke to someone from the Dutch railway agency. They had a weird peak in their train data at Amsterdam Airport around 2-3am almost every weekend. Turns out that hungry partygoers in Amsterdam took the train to the airport to go to the Burger King there, the only fastfood place that's open until 4am.