BlackBerry Z10 at the NYC Launch event, it came with OS 10.0.9.2372 installed. At that time I was unable to BBM video chat over my T-Mobile network, only via Wifi. Recently I had to get my Z10 replaced due to a weird rattle in the phone, and the new Z10 I was sent had a higher OS version 10.0.10.261. I was happily surprised to see that I was now able to enable BBM calls over mobile network:
Also, there has been recent leaked OS and official OS updates that are both versions higher than mine. I haven't been able to verify yet whether BBM calls over mobile network will work on those updates. If anyone is on T-Mobile and has a higher OS version than 10.0.10.261 running on their Z10, let me know in the comments below if the BBM calls over mobile network feature is working for you.