will try to follow up ambo categorys for you.. i can tell you now that cat1 and cat 2 are lights and sirens, for things like cardiac/respiratory arrest, collapses, trauma, heammoraging etc.. for example,, an MVA is a cat2...
cat3 is possibly something like a person with pain, discomfort or soem other minor illness.. but in no-immediate life threat, hence no lights or sirens...
cat 4/5/6 are differant levels of transfers i believe, couldnt tell you exactly how they are classed, but it is based on treatment required or not...
this is my interpretation only, as ebst i can remember it, but yeah no gaurantees.... however cat1's and cat2's are the exciting ones...