Rust is collecting quite a following and currently has no solution to the local package management + cache problem that artifactory solves.
This feature request would provide a way to mirror & cache crates.io whilst allowing for local publish of company specific packages.
The crates.io repository is here and specifically includes this warning:
"DISCLAIMER: The process of setting up a mirror is a work-in-progress and is likely to change. It is not currently recommended for mission-critical production use. It also requires a version of cargo newer than 0.13.0-nightly (f09ef68 2016-08-02); the version of cargo currently on rustc's beta channel fulfils this requirement and will be shipped with rustc 1.12.0 scheduled to be released on 2016-09-29."
so some work would probably be required to achieve this.
If you do decide to proceed with it then it's likely that you can get significant support from the rust community if you're willing to push changes back upstream to the crates.io project. Equally, my company will likely need to solve this problem ourselves and so it's possible that we could liaise with your engineers to speed things up or providing testing resource.