Arthur Season 12-15 episodes in 16:9 aspect ratio

On iTunes in Australia season 14 and 15 are in widescreen but season 12 and 13 are cropped to PAL widescreen (16:10). The widescreen episodes also lack the Word from Us Kids segments due to them not being filmed in widescreen or edited in widescreen.

On CBBC/BBC, the seasons that you listed aired in widescreen and some recordings of them made their way to Dailymotion. However it seems the encodes are extremely rare as no site that hosts TV shows lists them at all, just Dailymotion which hosts them. Some of the episodes are hosted on a Dailymotion account named "cBeebies Children Cartoon 02".

I was able to find the intro as well (which most encodes in widescreen cut off): www.youtube.com/watch?v=GRFqnRBAvLM