TriggerEvaluate(trig)

I noticed in bizzard.j ConditionalTriggerExecute(trig) calls function TriggerEvaluate(trig) which returns boolean. Anyone know exactly what it is checking?

TriggerEvaluate evaluates the trigger conditions.

Which means? You can use some other trigs conditions for what you want?
I've never really understood the whole trigger manipulation thingies.

it runs the trigger's condition and returns the condition return value or false if the condition is "returns nothing". I don't know what it does if you have multiple conditions, probably logical and with early escape, but no idea what that order is.
Trigger execute runs the trigger actions with out checking if conditions are true, so you can use TriggerEvaluate to make a trigger behave the way they do when triggered by events.