Combinar varias filas en una sola fila

Aquí está A forma de hacerlo (también funciona con 2005):

Mesa

DECLARE @table TABLE
    (
      [Type_ID] INT,
      [Client_ID] VARCHAR(50),
      [PBX_Vendor] VARCHAR(50)
    )

Datos

INSERT  INTO @table
        SELECT  127,
                '090820006311404926326C',
                'Aastra'
        UNION ALL
        SELECT  127,
                '090820006311404926326C',
                'Ericsson'
        UNION ALL
        SELECT  127,
                '111012237401404926326C',
                'Aastra'
        UNION ALL
        SELECT  127,
                '120209287521404926326C',
                'Aastra'
        UNION ALL
        SELECT  127,
                '120209287521404926326C',
                'Alcatel'

Consulta

SELECT  [Type_ID],
        [Client_ID],
        (
          SELECT    STUFF((
                            SELECT  ',' + [PBX_Vendor]
                            FROM    @table
                            WHERE   [Client_ID] = tbl.[Client_ID]
                                    AND [Type_ID] = tbl.[Type_ID]
                            GROUP BY [PBX_Vendor]
                            ORDER BY [PBX_Vendor]
                          FOR
                            XML PATH('')
                          ), 1, 1, '')
        ) PBX_Vendor
FROM    @table tbl
GROUP BY [Type_ID],
        [Client_ID]

Resultado

Type_ID     Client_ID               PBX_Vendor
127         090820006311404926326C  Aastra,Ericsson
127         111012237401404926326C  Aastra
127         120209287521404926326C  Aastra,Alcatel