Lionel have been using the 'trainz' trademark for decades, since at least the 80s IIRC.
Given that they're one of the biggest model train manufacturers in the US, if not the biggest at least the most well known, I'd be very weary about throwing around 'imposter' claims.
I guess it was just one of those things where Auran didn't think to check back in 2000 or whenever.