Factual error: The rabbits are underneath the landrover, and they get shot out the back whilst holding on to the axle. Land rovers have an enclosed axle with a hub enclosing the diff, so this would not be possible.
Factual error: Thomas McGregor asks at the station in London for a 'round trip' ticket to Windermere. It's called a 'return' in Britain and no British person would ask for anything else.
Answer: It's not clear if he actually can hear them or not. It's implied in the film that it's possibly stress or a mental break that is causing him to hallucinate their voices, or is suddenly thinking on a brain wave length that can understand them. If it's the former, it's coincidence that he hears similar to what Peter is actually saying. Either case explains why he suddenly can hear them when nobody else can around them despite them talking in front of people.
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