The CW Network makes all programming decisions regarding their programs. The CW Network programming airs Monday through Friday at 3:00p-4:00pm and 8:00p-10:00pm and Saturday mornings at 7:00a-12:00noon. The CW decides what day of the week and the time their shows will air. They also decide whether they will renew or cancel a program. The stations that carry CW programming have no input into these decisions.
The CW announced that 90210 and Emily Owens, M.D. will not return after this season. While The CW does not tell us all the details behind their decisions, the most likely reason is low viewership across the country (not just the Los Angeles area).
If you are unhappy with The CW’s decision, you can write to them directly at firstname.lastname@example.org and let them know.
The CW has made an early announcement that these shows have been picked up for another season: Bill Cunningham (season 3), Arrow (season 2), Supernatural (season 9), and The Vampire Diaries (season 5). More announcements will come in mid-May.