Once created, you can query the first point of a constuction xline using the BasePoint property. The second point used to create the xline is not stored with the object. Instead, use the DirectionVector property to obtain the directional vector for the xline.
This example finds the base point and directional vector for the xline created in
Dim BPoint As Variant
Dim Vector As Variant
BPoint = xlineObj.basePoint
Vector = xlineObj.DirectionVector