Actually, the trigger is still random chance - the SOS response just ups the mutation rate. An analogy for this type of situation might be a person confronted by a tiger. The normal response to this situation would be to run like hell, even if there is only, say, a 1/1000 chance of getting away and you're likely going to hurt yourself just running anyway (smacking into things, etc). The SOS response is the bacterial equivalent of a 'panic' button.
Not many antibiotics actually act by damaging DNA, but the point is valid. The only way that this type of SOS response could be said to be "intelligently designed" as opposed to evolving naturally, would be if a significant minority or a majority of bacteria could mutate a specific gene (ie, MDR) in response to an antibiotic that they do not encounter in nature (again, that would beg the question of WHY anybody would design bacteria that way, but we all know what the answer to this question would be).
This type of response is equivalent to the ability to form spores - a trait that has served the bacterial ancestors well in the past during times of great stress. This is a surprising finding but also fairly in line with common sense - the way a whole lot of discoveries in biology are.