As a non-lawyer, I tend to agree with MoJo in this. I note that in the first paragraph of 2510.3-102, says, (my emphasis) (a)(1) General rule. For purposes of subtitle A and parts 1 and 4 of subtitle B of title I of ERISA and section 4975 of the Internal Revenue Code only (but without any implication for and may not be relied upon to bar criminal prosecutions under 18 U.S.C. 664), the assets of the plan include amounts (other than union dues) that a participant or beneficiary pays to an employer, or amounts that a participant has withheld from his wages by an employer, for contribution or repayment of a participant loan to the plan, as of the earliest date on which such contributions or repayments can reasonably be segregated from the employer's general assets.
Now, I don't know what that really means in real life circumstances, but it does seem to indicate that the exemption isn't "blanket" and may only be relied upon for specific purposes. But as I said, I'm not a lawyer, so this is nothing more than useless speculation on my part. It's fun to randomly talk about things I know nothing about, when I can't be held responsible for what I say. I think that qualifies me to run for President.