Fn::ImportValue from other stacks

One import via join.yaml

      Tags:
      - Key: Name
        Value:
          !Join ['_', [ ec2, "Fn::ImportValue" : {"Fn::Sub":'${BaseStackName}-Environment'}, test2]]
          #This will create a name tag with value: ec2_<yourValueFromOtherStack>_test2

One import+one local ref via join.yaml

##This is untested, i created this from One import via join.yaml to give you an example with one import and one local stack ref
      Tags:
      - Key: Name
        Value:
          !Join ['_', [ ec2, "Fn::ImportValue" : {"Fn::Sub":'${BaseStackName}-Value'}, "Fn::Sub":'${ValueFromThisStack}', test2]]
          #This will create a name tag with value: ec2_<yourValueFromOtherStack>_<valueFromThisStack>_test2

One import+one local ref via Sub.yaml

     Tags:
     - Key: Name
        Value: !Sub
        - ec2_${ValueFromBaseStack}_${ValueFromThisStack}_test2
        - ValueFromBaseStack:
            Fn::ImportValue: !Sub ${BaseStackName}-Value
     #This will create a name tag with value: ec2_<yourValueFromOtherStack>_<valueFromThisStack>_test2

Thank you!