Assets arising during money purchase pension plans retain many interesting features in later years, even after the money purchase pension plans have gotten merged into profit-sharing plans or 401(k) plans.

Do the J&S and no-in-service-withdrawal features apply in remote years to interest and dividends that emanate from assets attained during the money purchase pension plan years?

Can someone provide a citation from official literature regarding this?

Any other information on merging money purchase pension plans into 401(k) plans or profit-sharing plans would help.

Take a look at

Revenue Ruling 94-76, IRB 1994-50,5, November 29, 1994: the merger "does not divest the assets and liabilities of the money purchase pension plan of their attributes as pension plan assets and liabilities. Therefore, to satisfy §401(a), the assets and liabilities transferred from Plan A to Plan B must remain subject to the restrictions on distributions applicable to a qualified money purchase pension plan. In order to remain qualified, any plan provision applicable to the accrued benefits derived from Plan A must not permit distributions prior to retirement, death, disability, severance of employment, or termination of the plan. Plan B's distribution provisions permit distribution of an employee's accrued benefit after two years."

and

Revenue Ruling 2002-42, 2002-2 CB 76, IRB 2002-28, 76, June 17, 2002: "The holding in Rev. Rul. 94-76 is applicable when an employer converts a money purchase pension plan into a profit-sharing plan."

While the merger is not tantamount to a termination of the MPPP that would trigger immediate, 100% vesting, you must give a 204h notice in advance of the merger (or earlier date when MPP accruals will cease).

If you terminate the MPPP instead, then all would be 100% vested, but then any amounts that the employees choose (with spousal consents as necessary) to roll into the PSP would be cleansed of those pension attributes (except to the extent provided by the PSP).