The UPX twitter account just
posted: "Bicycles are permitted on UP Express during non-rush hour times. No Bicycles between 6-10am and 3-7pm, Monday to Friday."
Last time I checked, UPX completely prohibited bicycles at all times (except, I think, folding bicycles). I guess this was one of the unannounced side-effects of the recent change to make their service more GO-like/commuter-friendly? Hadn't heard it mentioned before.
Edit: a google search revealed an
archived UPX document that stated "Bicycles are not permitted on UP Express unless they are dismantled and packaged similar to airline requirements. Note that foldable-style bicycles, once folded up, are allowed on all UP Express trains." So yes, it seems that this was a recent change. I would naturally assume that dismantled+packaged, or folded, bicycles are still allowed during peak hours/in luggage.