And here it is: https://sourceforge.net/projects/ardurail/
Until now we haven't released any files but you can check out the (hopefully) working development version from SVN. The last changes I made were to put the whole code into a class so that it later can be distributed as a simple library. Also I added some functions for better control of the devices.
The next step will be (after testing the actual code): Writing a derived class which implements the P50 protocol (currently it is a method inside the class) and than a derived class for SRCP (see http://srcpd.sourceforge.net/srcp/).