** Shares of British public transport operator FirstGroup FGP.L up 3.43% at 181.9 p, among top gainers on London's mid caps index .FTMC, which is down 0.17%
** Co announces that it was named as preferred operator for London Overground rail contract
** FGP estimates the contract at 3 billion pounds ($4 billion) over eight years
** Co says contract's initial term is eight years with an option to extend for up to two additional years
** Up to Tuesday's close, stock had risen 8.76%, compared with a 6.10% YTD increase in FTMC
($1 = 0.7507 pounds)
(Reporting by Simone Lobo in Bengaluru)
((Simone.Lobo@thomsonreuters.com, +919920570373))