Show me a link where the Orioles fired Brooks. They may have let his contract run it's course, but I don't think he was fired. The only way Palmer gets fired is if he gets caught up in something stupid. (Says something awful on the air, gets arrested, etc.) They aren't going to fire a guy who has a statue in left field because he's lost a step or two in the booth.
One season he worked for them, and then the next season he didn't. I guess you can split hairs on what you call it, but I'm guessing Brooks felt like he was fired.