I'm trying to revive the bike sub-form because it just seems so gloomy as of late!
I'll share my own, short-lived experience with bike on train.
After doing much research with Mobile01, Facebook groups and reading through the Op's posted blog, without a bike bag of any sort in hand, I decided to jump on the local train from Hsin Chu to Song Shan station. I went to the counter to purchase my full ticket for me and half ticket for my bike and was stopped by the girl at the counter saying that, if it wasn't bagged, it's allowed on the local train. She then told me there's a local train I can board that's arriving in 4 hours. However, I have to register to get on. More bad news, she couldn't guarantee it because it's limited space.
At this point, I just felt let down. I couldn't blame the girl behind the counter, she was just following protocol. A lot of people were saying that taking a full sized bike on the train, unfolded and unbagged is do-able. I've seen pictures of people bringing bike unbagged on local trains. I guess I was just unlucky?
I went back to my friend's apartment afterwards and we discussed it's probably because I was getting on and off at two major stations and it may also depend on the person behind the counter was having a good or bad day.