Is there any sort of agreed-upon format for MBX games like there is for CPX games?
Not really. Unlike CPX games which have developed their own language for efficiency purposes (“oo” for “orders out,” for example), MBX games have no real set protocol. Thus, every MBX tends to be quite different from another, the main difference being the style of writing in the sighting and combat reports, which can often be a reflection of the personality or knowledgeability of the umpire. So there are probably as many styles or formats of MBX games as there are MBX umpires. If you would like to know more about the format for an MBX you are interested in, ask the umpire before signing up.