TWELVE retiring expatriate civil servants will go home on the luxurious liner Canberra next March, at a cost to taxpayers of at least $400,000. The dozen might be among the last civil servants to enjoy the sunshine on the liner, because the Government proposed last year to scrap the fringe benefit, which it considered outdated. Although the Government declined to disclose how many officers would take the passage next year, P&O Travel, the agent for the Canberra in Hong Kong, revealed that 12 expatriate civil servants had made reservations. There were 26 listed fares, and a spokesman for the agency said civil servants usually chose fares between $33,922 and $56,731, depending on the room sizes and facilities. The director of the agency, Richard Willis, said the ship would leave Hong Kong on March 9, 1994. A dispute between the Government and civil servants broke out after the administration announced its proposal to scrap the sea passage perk. Civil service unions and legislators claimed that the administration would be in breach of employment contracts if it unilaterally scrapped it. The Government has offered a number of alternatives, including first-class air tickets home or unspecified ex gratia payments. But civil servants rejected these options. Twenty-eight expats sailed home this March.