The AxisAlignedRectangles property is a property of type PositionedObjectList. Therefore, you can use this member the same way you would use a PositionedObjectList<AxisAlignedRectangle>.
Code Example
The following shows how to loop through all rectangles in a ShapeCollection and perform collision between the rectangles and a Circle named CircleInstance:
for(int i = 0; i < ShapeCollectionInstance.AxisAlignedRectangles.Count; i++)
{
circle.CollideAgainstMove(ShapeCollectionInstance.AxisAlignedRectangles[i], 0, 1);
}