My personal opinion on this is "only barely - if at all". If you can read German then Jens Coldewey's very good summary of the problems you run into if you try is just for you. Here is my adhoc translation of a section in which he characterizes his experience with refactoring large C++ legacy systems:
To rework and refactor a whole system like this can take years. Languages that enforce such big rework should not be used anymore except in very special circumstances. Would you buy a new car the engine of which was developed in 1980 and which contains many concepts of his 1960 precessor?