These are all straw man arguments; there is no parking lot being contributed, no employer securities. There is a check being sent in just like they employer always does. The trustee will accept that as always. In fact, it is unlikely to even pass through the trustee as the employer writes the check to the funding agency for deposit into the account (like, Fidelity, Merrill Lynch, etc.). There is no language in this plan that violates any federal law (another straw man argument not germane to this case). The issue is clearly if a CBA external to a plan can change the terms of the plan. Barring any language in the plan that incorporate by reference (and we know this one DOES NOT), the answer is a clear cut NO.
And I don't agree that everyone agrees the contribution required by the CBS must somehow be made to the plan. The employer can go back to the union and renegotiate to make up the missed contribution by cash payments to the participants if the parties agree. So, no matter how you define "takes precedence", the CBA does NOT do so with regard to the plan. Not no way, not no how.