The MSCL isn't quite smart enough to manage this sort of thing
The Lutron MSCL was designed for applications where a single sensor can cover the entire space, but multi-way dimming control is still necessary (say, a modest-sized room with multiple entrances). As thus, there's no way to use a "remote sensor" with the MSCL, just a standard Lutron Maestro dimming remote, which isn't quite what you want.
However, there is a way to do this
Fortunately for you though, with the use of two gangs of junction box space at each location, it should be possible to do what you want in a smoothly integrated way. As it turns out, the Leviton Vizia dimming system interoperates with the Leviton IPP series occupancy/vacancy sensors -- this not only allows Vizia remotes to be used to provide multi-way switching with a single occupancy sensor, but allows the IPP0R remote sensor to be used as a matching remote in the Vizia system.
In this setup, the box with the load wire in it gets a Vizia dimmer (VZM10 depicted, but any Vizia dimmer will do) and an IPP0R remote, while the box with the line wire in it gets a Vizia matching remote and an IPP0R remote. Keep in mind that this cannot be extended to a 3rd location without sacrificing dimming or motion sensing at that location (the Vizia system supports 4 matching remotes on a single master, maximum), and that the neutral wire needs to be present at both boxes for this (it is possible to wire this if line and load come in at the same switch box by making the white wire neutral once more, but not if power comes in at the light fixture). See the diagram below for details -- note that the dashed red lines in the diagram represent the red/yellow wire pigtails present on Vizia dimmers and remotes that use wire pigtails, or a field-fitted pigtail (of any suitable color) connected to the terminal marked RD/YL on Vizia dimmers and remotes that use screw terminals.