Having a compatibility layer alone is far from sufficient. BBOS 10 (at least on the Z30) was downright miserable to use. There was also a huge open source developer community surrounding Maemo/Meego that I'm not sure BBOS has ever seen.
I had multiple Maemo devices — the 770, 800 and N900 tablets.
I really tried hard to like the system, but let's not exaggerate its strengths. The open source software was mostly amateur ports from desktop Linux.
I remember back in 2008 demoing my Nokia 800 mini tablet to someone who had got a brand new iPhone 3G. There just wasn't any contest. The Maemo software felt like a product of the '90s, and the hardware clearly wasn't by Nokia's "A Team".
I completely agree about the software on Hildon based Maemo devices, but Meego on the N9 (Harmattan/QT based) was downright gorgeous, and managed to see some quality official apps for services like Facebook, Twitter, and Spotify.
I just switched from my final BlackBerry after 10 years in the B.B. ecosystem to an iPhone X. The Android app compatibility extended the life of my Classic for an extra year but was hamstrung by being painfully slow. I could run Spotify or Google Maps but only just so, and forget about multitasking.
I still miss the BB10 workflow. Messaging, multitasking, swiping was all perfected ahead of the mediocre implementation of those in iOS 11, but the X is so fast, I can just brute force my way around the UI gaps and get shit done more quickly.
Nokia was coming from a similar position as BlackBerry, so I don't see how it would have worked for them either.