I don't know anything about ABC, but generally speaking, I imagine that the likelihood of a media company's internal team declaring that their own company's reporting is biased is about as likely as BP creating an internal team that reports offshore drilling creates uncontainable environmental risks.
I don't think it's surprising that the majority of established media companies lean in a certain political direction. People on one side of the political spectrum may be more attracted to journalism than the other side, which would naturally lead to media companies producing journalism more sympathetic to the political arguments that their employees are sympathetic to.
No-one can be unbiased about the news because it's inherently subjective. I agree, an internal-only team can't help but be biased, which is why they try to balance it against an external team.
I don't think it's surprising that the majority of established media companies lean in a certain political direction. People on one side of the political spectrum may be more attracted to journalism than the other side, which would naturally lead to media companies producing journalism more sympathetic to the political arguments that their employees are sympathetic to.