Whomever told you that has a very limited knowledge about cIOS'es. "249" is a slot number. Whether it runs black ops or not depends on what cIOS you install to it.
Most recent guides nowadays advice to install rev21 with a base IOS of 56 in 249 (these are options you have to choose when installing Waninkoko's latest revision). This is because most loaders see this number as a default value for a cIOS (and it's true: pretty much all softmodded wii's have "a cIOS" in that slot) and base IOS 56 has roughly the best compatibility.
Black ops, on the other hand, is one of the exceptions: it needs base IOS 57. I advice you to install that in another slot (248 perhaps?), and tell your loader to use this cIOS for black ops. I certainly wouldn't overwrite 249, or it'll cause problems with other games.