Business Associate Agreement - Signature?

[Guest tintree73]

What is the ability of the plan administrator of the plan (the plan is the covered entity) to sign the business associate agreement with a TPA? Also, if the contract provides for services other than those covered by the Business Associate agreement (e.g., provides for services for the employer to use for its HR function): (1) may Business Associate portions be part of the agreement - one section, (2) may the agreement be structure to have provisions 1-8 (non-BA provisions) binding on the Plan Sponsor (or employer) and the 9th provision (BA provisions) to be binding the plan with the plan administrator signing along with the TPA, and (3) then make the employer/plan sponsor, plan administrator and the TPA all sign the agreement?

Help!