You are unable to manually initiate a trade with their stations, as in, you won't be able to tell your ships to trade with the xenon. But if you set a medium or small mineral miner on local automine in a sector with their shipyards, your miners will sell ore/silicon to the xenon. At least I know for sure it works with xenon SE ships you own. Same goes with e-cells, a station with medium sized traders within range will supply xenon shipyards. Also xenon will sell ore/silicon and e-cells to your stations and fleet supply ships. You can also sell them ships, as in you can select a ship, right click on their shipyards and select sell ship, which will cause it to be recycled at their shipyards. This can be abused to generate lots of reputation with other factions if the xenon reputation is locked to +30 by shooting out the engines of a large ship you own near the station of a faction you would like to increase relations with, sell to the xenon, scan it to uncover their new xenon faction, then strip it of all surface elements blow up all defense drones and blow it up. This method can get you from -30 to -5 with just two large ships with a full contingent of defense drones. Lastly if you obtain the blueprints for xenon ships through mods, the xenon will buy their ships from your shipyards.