The failed rescue operation caused a diplomatic row between Britain and Italy after Italian president Giorgio Napolitano said it was "inexplicable" that Downing Street had not alerted Rome to the plan to rescue the men in advance.
But Foreign Secretary William Hague insisted it had been impossible to inform the Italian authorities in advance.
Mr McManus, 28, was working for the construction company B.Stabilini when he was kidnapped on May 12 by gunmen who stormed his apartment in the city of Birnin-Kebbi, about 110 miles away from Sokoto.
Mr Lamolinara was also abducted. A German colleague managed to escape by scaling a wall, but a Nigerian engineer was shot and wounded.
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The maintenance worker spent 10 days in hospital after plunging 9.5 metres from a scaffold tower at a disused station.
Workers and managers are to stage another strike on Saturday amid a long-running dispute over jobs, pensions and closures.
The unexpected call could prompt a diplomatic rift with China, which regards Taiwan as a breakaway province from its mainland.