Tertiary Liability in 4204 Transaction

[Guest BenefitsBob]

Seller S sells its assets to buyer B1 in a 4204 transaction. In connection with the transaction, pursuant to ERISA Section 4204, S agrees to remain secondarily liable for a withdrawal by B1 during the 5 years following the closing of the transaction. On the first anniversary of the transaction, B1 sells its assets to B2 pursuant to a 4204 transaction. Pursuant to ERISA Section 4204, B1 agrees to remain secondarily liable for a withdrawal by B2 during the 5 years following the closing of the transaction.

Question: Does S remain "tertiarily" liable for a withdrawal by B2 during the four year period following the closing of the sale of B1s assets to B2? Any support for the answer?

PBGC Opinion letter 90-1 does not speak to this issue.

Thanks in advance.