Here is a solution that works in SQL Server 2005+:
SELECT t.TicketID,
STUFF(ISNULL((SELECT ', ' + x.Person
FROM @Tickets x
WHERE x.TicketID = t.TicketID
GROUP BY x.Person
FOR XML PATH (''), TYPE).value('.','VARCHAR(max)'), ''), 1, 2, '') [No Preceeding Comma],
ISNULL((SELECT ', ' + x.Person
FROM @Tickets x
WHERE x.TicketID = t.TicketID
GROUP BY x.Person
FOR XML PATH (''), TYPE).value('.','VARCHAR(max)'), '') [Preceeding Comma If Not Empty]
FROM @Tickets t
GROUP BY t.TicketID
Reference: