I don't think I would chance it myself but I am one who tends to follow the rules.
I would be worried that they would search your bag and not let you on at all. And I would add, that maybe they have the rule because of people with allergies? I'm allergic to cats and would not be happy if the person next to me on the train had a cat in her bag..... just my opinion. Let us know how you make out though if you do decide to chance it.
