Do multiple Python interpreters on a server share pages in memory?
Not on purpose. They let the OS worry about sharing pages between the instances of the library.
One of the more clever things Android does to conserve memory and increase startup time is share pages between multiple Dalvik interpreters by forking processes from a the zygote process. When an application loads, the static, readonly library code pages are shared between the parent and the child. 
Does python or multiprocessing do anything on these lines?