1. Create your project plan template containing your standard milestones.
2. Customize Flag1 to denote which milestones you want to evaluate.  You can rename the field to be more apparent as to it's purpose if you like.  The formulas below will use the original name. 
3. Customize Date2 to use the following formula.  This formula puts the finish date of the current phase milestone into this field.  Make sure you set the rollup the Maximum value or you won't get the correct value at the Project Summary task level.
   IIf([Flag1]=Yes And [Finish]>DateValue([Current Date]) And [% Complete]<>100
   And [% Complete]>0,ProjDateValue([Finish]),ProjDateValue('NA'))
4. Customize Text 1 with the following formula.  This retrieves the name description of the current phase milestone.
   IIf(ProjDateValue([Date2])<>ProjDateValue('NA') And [Summary]=No,[Name],"") 
5. Temporarily add Flag1 to your view.
6. Mark the milestones in your Project Plan to evaluate by setting the value of Flag1.
7. Since a macro is used, macro security must be set to either Medium or Low for execution to occur.  I recommend Medium since that provides the user with a measure of control when opening unfamilar project plans.  To set the macro security, in Project Pro, go to Tools, Macro, Macro Security and set the value appropriately.  You may also want to restart Project as a prudent measure.
8. Lastly, add the following macro code to move the Text 1 value to the Project Summary rollup.  To do this, press Alt+F11. The macro code needs to be added in the "ThisProject" entry under VBAProject([name of open project]), Microsoft Project Objects should be selected in the left pane.  Select it if it is not already open.  Paste in the code below.
   
   Private Sub Project_BeforeSave(ByVal pj As MSProject.Project)
   
   Dim t As Task
   On Error GoTo ErrorHandler
   
   Application.CalculateAll
   
   For Each t In ActiveProject.Tasks
       If t.Text1 <> "" Then
           SetTaskField Field:="Text1", Value:=t.Text1, TaskID:="0"
       End If
   Next t
   
   GoTo EndSub
   
   ErrorHandler:
   
       MsgBox Prompt:="Error Number: " & Err.Number, Buttons:=vbCritical, _
       Title:="Set of Milestone To Summary Level Macro Error"
      
   EndSub:
   End Sub
   
9. Save the project. 
10. If you autopublish, the values will get published to PWA automatically.  Otherwise, you have to remember to publish.
11. Go to PWA and create a Project Center view that has the Date1 and Text1 in it.  You can select the names that you renamed the fields to, but you have to make sure that all of the projects in the view have the same field rename.  Otherwise, you may get some strange results.
12. If you did everything above, you should see your desired data.

Enjoy!