Simplify the following text for a Grade 19 native English-speaking person.
Original: Depending on their agreement , or agreements , with their local ambulance service trust ( known as a Memorandum of Understanding or MOU ) , they may treat and transport certain categories of patient to hospital , although for more serious incidents , such as cardiac arrest it is likely that they would be expected to summon the assistance of the statutory ambulance service .
Simplified: Depending on their agreement\/s with their local ambulance service trust ( known as a `` Memorandum of Understanding '' or MOU ) , they may treat and transport certain categories of patient to hospital , although for more serious incidents , such as cardiac arrest it is likely that they would be expected to summon the assistance of the statutory ambulance service .