One of the values of Esperanto is as a learning tool for Western European languages--according to one study, students with 1yr Esperanto + 3yr French instructio

One of the values of Esperanto is as a learning tool for Western European languages--according to one study, students with 1yr Esperanto + 3yr French instruction speak better French than students with 4yr French instruction. Since I am about to start learning Bulgarian, I am particularly interested to know if this language has similar properties with respect to Slavic languages. Obviously since it's only been around since 2006 there isn't a comparable 4-year study, but even anecdotal evidence would be appreciated.