As a teacher I occasionally use cbeebies to help with my teaching, we watched an episode of "do you know" this term to find out about something we were learning about.
It's rare though, maybe twice a term maximum, and always for educational reasons.
Perhaps the Bing episode was used to cover a friendship issue or something to discuss at circle time?
However, two or three times a week seems extreme, even if it is being used to help with teaching.
Is it definitely happening in lesson time and not at wet play? It might occasionally happen during free time, but I'd argue that should be rare as children need (and there is real value in) time for unstructured play, not just a break in front of the TV. My golden time on a Friday is only ever a DVD or a film right at the end of term, and only if the children choose it, which they often don't!
I'd raise it with the class teacher, or possibly the deputy head? Do so in a non confrontational way, just mention it as a concern and she/he will look into it, I'm sure.