May a Qualified Termination Administrator wind up a portion of a retirement plan?

The Labor department’s rule about an abandoned individual-account retirement plan defines a qualified termination administrator as a bank, trust company, insurance company, or other person eligible to serve as an IRA’s custodian that “holds assets of the plan that is considered abandoned[.]”  29 C.F.R. § 2578.1(g)(2).  The rule does not say that a QTA must hold all, or even substantially all, of the plan’s assets.

Imagine an abandoned plan for which no QTA-eligible company serves as a trustee.  There are multiple custodians.  Imagine one would volunteer to serve as a QTA, but only for the assets held by that custodian.

Has anyone seen a situation in which the Employee Benefits Security Administration approved, or did not object to, a submission in which a QTA proposed to wind up a portion of a plan to the extent of the assets held by the QTA?

As I skim the rest of the QTA rule, it seems to preclude a wind-up administration if the QTA-eligible custodian knows it holds less than substantially all of the plan’s assets (other than contributions owed to the plan) and is unwilling to serve as QTA for the whole plan.