Is the Value Plus Plan eligible for the Trade-in/ Upgrade Promotion?

No.  It is specifically excluded on ever written offer.  And if you try to order a phone with the unlimited value plan, you will get a warning as shown in the picture below that your plan is not eligible for the promotion.

The written offer also says both of the following...

@formerlyknownas , thanks for the info.  I realize that there are multiple promotions out there with terms and conditions listed. Unfortunately, I did not save the posted promotion at the time of my trade in process, and @ATTHelp was not willing to supply the promotion, as written, at the time of the transaction.

However, from the Phone Trade In - Find Out What Your Device is Worth - AT&T   https://tradein.att.com/offer-details

Promotion Details as of December 28 , 2022:
  "Retired unlimited plans may also qualify (excluding prepaid, session-based, and Data Unlimited at $45/mo. plans)." My Value Plus plan was indeed more than $45/mo.

So, in hopes that my plan "may" qualify, I contacted customer support. On two different occasions the rep informed me that my plan does qualify and they would push it through. In each case, the deal did not get resolved. Therein lies my frustration.

You are misreading that. It says “excluding prepaid, session-based, and Data Unlimited at $45/mo. plans”. That means the grandfathered Data Unlimited at $45/mo is also excluded. On top of that, your value plan is a current plan, not a retired plan. Your plan does not qualify. Any rep telling you it does is just plain wrong. You have every right to be frustrated.

You can't look for details to include, when you have been put on a plan which is specifically excluded from every single phone deal by name. There is no wiggle room or confusion. 

One of the requirements is that you be on an unlimited data plan with a base price of $75 or more for one line and you're not.

   The unlimited Value Plus plan is specifically listed as being excluded from the phone deals. It is a relatively new plan and it has been excluded from every single phone deal ( just like Verizon's welcome unlimited plan is excluded, which is their bargain Unlimited)

https://consumercomplaints.fcc.gov/hc/en-us

Don’t listen to these “Aces”, they are just going to tell you over and over that it is your fault. If AT&T was interested in dealing fairly with their customers they would not allow you order a phone without the qualifying plan, leaving you trying to figure it out months later. Contact the FCC.

Actually we didn't say it was his fault. We have indicated he was lied to. Unfortunately it doesn't make any difference if he's on the wrong plan

@HeywoodJablome 

BTW... 

As pictured earlier, it is not possible to check out with the wrong plan and think you are still getting the deal when there is a warning. The top picture shows check out with the Value Plus plan. The bottom picture shows check out with a qualifying unlimited plan. 

I am dealing with the same issue. However I haven't bought or traded a new phone. I need to upgrade my 2018 LG phone and at&t tells my that I need to upgrade my value plus plan to be eligible for any of their promotions. It's just not right!