Theres no reason why somebody who has used any of these languages would not understand C++ code.
I dont know... C++ has an automatic memory management system (RAII) that is quite different from other languages (especially ones needing a GC). Even though developers new to C++ may be able to understand what the C++ code does, I don't know if I would trust that their code is safe and correct.
But I could be wrong. Apple has proven that if you make a language trendy and cool enough (Objective-C), no matter how low level and complex it is*, even beginner developers are very capable and productive regardless. Better still, many beginner developers are quite happily cross compiling to restrictive ARM devices and remote debugging. Something that is quite a step up from what I was doing when I was starting out (VB6) ;)
* no garbage collector (Apple deprecated it), pointers, possible undefined functionality, exposure to C-style memory management.