Two construction companies, a designer and a contractor with major footholds in South Africa, take somewhat different views of the country’s market prospects in these tougher economic times. Photo: Mott MacDonald Mott MacDonald, which designed the innovative roof of South Africa’s Mbombela soccer stadium, site of the World Cup in June, is bullish about regional growth. U.K.-based Mott MacDonald Group, London, accelerated its upward trajectory in South Africa last month by announcing its acquisition of the Johannesburg-based power-sector designer Merz and McLellan Pty. Ltd. The 45-person firm, with offices in South Africa and Botswana, has been a player in the