Rough watch, probably won't watch again, and can't confidently recommend, unless it's for younger audiences...and even then, probably no.
This movie feels like a first attempt. Tad is actually a charming underdog character, Sarah plays well as an attraction for the lead and an independently grown character which shows so much intricacy from a writing perspective that the rest of the non-animal characters are baffling.
There is just so little here to work with that I don't have a lot to say. The train action sequence was actually decent, but I was wasn't engaged with the movie for the majority of the time.
I think this is better skipped, but if you actually like this, then there is a sequel that is slightly better.