Returning text from a BR# inside GetDataCell — possible?

You might consider doing this via dynamic calc member instead. There is a 'annotations consolidation' snippet example available to build from. The example is a UD8 member but you could create a dynamic calc member in a different UD dim.

'Cube View definition
'Row Definition:  E#[Total GolfStream].tree
'Col1 Definition:  V#Annotation:Name("Comment")
'Col2 Definition:  V#Annotation:UD8#DynamicTextCons:Name("Consolidated")

'UD8 Member setup
'Name:     DynamicTextCons   <-- If this is changed it must be updated in the CV Col2 definition above.
'Formula Type:   DynamicCalc
'Allow Input:   True
'Is Consolidated:  False
'In Use:    True

'Assign the  formula below to the UD8 member to show the consolidated text
Dim iEntityID As Integer = api.pov.Entity.MemberId
Dim iETestID As Integer
Dim strETestName As String = string.empty
Dim eTest As Member
Dim sSave As String = string.empty
Dim sSource As String = string.empty

If api.View.IsAnnotationType Then
 If api.Entity.HasChildren() Then

  For Each etest In api.Members.GetDescendents(api.Dimensions.GetBaseDim(dimtypeid.Entity).DimPk, iEntityID)
   iETestID = etest.MemberId
   sSource = api.Data.GetDataCellEx("U8#None:E#[" & etest.Name & "]:C#" & api.Entity.GetLocalCurrency(iETestID).Name).DataCellAnnotation
 
   If Not sSource.Equals(String.Empty) Then
    sSave = sSave.Trim & "; " & eTest.Name & ": " & sSource
   End If
  Next
 Else

  sSource = api.Data.GetDataCellEx("U8#None:E#[" & api.pov.entity.Name & "]").DataCellAnnotation
  If Not sSource.Equals(String.Empty) Then
   sSave = ";" & sSource
  End If
 End If
End If

If Not sSave.Equals(String.Empty) Then
 Return right(sSave, len(sSave)-1).Trim
Else
 Return Nothing
End If