I've now seen Rainbow Roadtrip.* It will be a little while before I get it reviewed here, though, partly because I want to watch it again and 60 minutes of Pony obviously takes longer to rewatch than 22 minutes! I also endured a nightmare journey home yesterday in 32 °C heat with the railways falling apart around me, so I was simply too exhausted to do anything about the special until this afternoon.
* Italics rather than quotes as it feels like a cut-down film to me, rather than a lengthened episode.