my limited understanding is that the attachment disorder genesis discussion is more focused what happens childhood. Inappropriate parenting can damage the attachment system and a child of a BPD parent is exposed to some specific inappropriate parenting behaviors and through them is at some risk.
BPD is a lot about relationships once the person has matured to an adult and so attachment dynamics themselves (as aspect of relationship) are an important concept. Problems with attachment sure can add to the dysfunction in the relationship but are certainly not the sole reason for the roller-coaster. And on the other side of the curb attachment problems may linked with the difficulties to let go in the face of overwhelming facts from the non side.
If you are interested more in attachment / BPD related questions you may want to spend some time listening to this audio:http://www.borderlinepersonalitydisorder.com/audio-pres.shtml
scroll down to:
International Perspectives on the Treatment of Borderline Personality Disorder: U.K.
Anthony W. Bateman, MD
Developmental Considerations in the Personality Disorders
Early Childhood abuse as etiological and serious health risk factors in borderline patients:
An Attachment Perspective on Personality Disorder
Howard Steele, PhD