One of the advantages of CF is that you can very precisely and individually engineer the failure points. This is less true in other materials, where the strength may be more consistent throughout: overbuilt in some areas and under-built in others. The weight limit is only there if the manufacturer decided it should be, to make the bike lighter for the bulk of the market, or if they screwed up. CF was a huge breakthrough in racing sailboat construction, because of the aforementioned characteristics. If it can be used to withstand those forces I guarantee you it can used to make handlebars able to withstand Mark Cavendish's sprint forces. It's just a question of how strong the designer/builder decided to make it.