MAI Basic Four said it completed its $146-million reacquisition of two businesses that it sold to Bell Atlantic in 1985--MAI Canada Ltd. and the MAI Basic Four computer maintenance operations of Sorbus. The two businesses employ 1,100 people and will increase MAI Basic's worldwide work force to 4,500. MAI Basic, a Tustin-based computer company, said the businesses are expected to contribute $28 million to $30 million in operating income and $90 million to $95 million in net revenues during the next 12 months. The Tustin firm reported earnings of $22.8 million on revenues of $321 million for its fiscal year ended last September. MAI Basic said it is financing the acquisition through loans provided by a banking syndicate led by Toronto-based Canadian Imperial Bank of Commerce.