For any rule I'd argue that most good reasons to break or bend it are also good reasons to change it or make codified exceptions to it.
If I'm not tasked with enforcing rules then I probably don't care enough to complain if what you're doing doesn't affect me or someone else in an unlawful manner. If I got on the bus and you're snorting coke with your Husky laying at your feet I'm just going to sit there until it's time to get off the bus.
The 80 lb dog was an example. If you as a customer facing employee that gets seen by several hundred people a day noticeably breaks a rule there will be someone in that crowd that will refuse to comprehend that their situation is different than what you did for someone else. And I guarantee (from anecdotal evidence) that someone will try to get you in trouble if you break a rule for someone else and not them.
For this specific instance OP needs to be at the train station by a certain time and then on to Dallas. People are telling OP to just get on the bus and hope the bus driver doesn't care. That's really bad advice for something as time sensitive as train tickets and appointments in Dallas. OP will have to get lucky enough to not get a bus driver that's jaded like me when it comes to breaking the rules of my job for people that I will never see again but can cause me so much stress if I do do them a favor.