I helped set up mentor programs for incoming engineers and found the programs to be extremely successful. Not only does it promote good engineering practices, but the engineers feel like they are part of the team, and will stay with the team longer than the companies that do not have a mentor program.
At some companies, software engineers and system engineers are isolated from each other, and do not know how the two teams are actually one team. I have been part of two different types of mentor programs. One where we concentrated on only our software engineers, and one where software and systems worked together implementing a mentor program.
The software only program, just as the title implies was mentoring the incoming engineers in the software process, from analysis through test and integration. It is a good program and helps develop good softare engineers.