[boost] question regarding basic_stream::imbue

I have a simple question regarding basic_stream::imbue(locale &) Can it be applied after a file is opened? The state saver libray seems to suggest that it can. Some information suggests that it can if the file is position at the start. Experience with dinkumware and STLport suggests that it can't. If it can't what's the best way to work around it? Robert Ramey