MCI Communications Corp. is expected to announce as early as today that British phone company Cable & Wireless agreed to buy all of its Internet operations for $1.5 billion to $2 billion in cash, according to sources familiar with the companies' plans. Simultaneously, the Justice Department is expected to approve MCI's $46.5-billion sale to Jackson, Miss.-based WorldCom Inc., the sources said. The sale of MCI's Internet business was a condition for meeting regulators' demands. Washington-based MCI declined to comment. In the deal, which Cable & Wireless said last month it was negotiating, the firm would get MCI's 1,300 wholesale customers that resell Internet services in 76 countries as well as MCI's retail consumer and business Internet customers.