Ok here we go. Here is the description of the process and some MEL scrips and icons for a Maya shelf to help speed it up. I couldn't get the MEL export to work, it doesn't seem to allow for the population of 2 attributes that are required, so I've reverted to the way I know it works, and it's pretty simple. I did mine from scratch just now to make sure each step works.
LETS GO!!!!
So here I've got my 2 geos in Maya, specifically we have our scalp geo on which to place Xgen curves
This is the type of groom I made, Groomable Splines

- Capture1.PNG (62.54 KiB) Viewed 3415 times
You can see here the horrendous haircut I gave our PolyModel and our associated "collection" description.
Lets bring this into Clarisse
Now select the "Generate" top menu in Maya, and with the Description selected in the Outliner, select "convert to interactive groom"
A requester will come up, you can leave it blank, I did, and just hit convert.
That process will generate a new asset in your outliner

- Capture4.PNG (7.86 KiB) Viewed 3415 times
With that new asset selected run the following script
Here is the Icon I made for my custom Maya shelf

- XGenInteractiveGroomDescription_Export_Alembic.png (3.72 KiB) Viewed 3415 times
string $array[] = `ls -sl`;
for ($item in $array)
{
xgmSplineCacheExportCmd -export;
};
This will bring up the export dialog, make sure MULTIPLE TRANSFORM and WRITE FINAL WIDTH are turned on
(this is what was missing in the MEL export, and it is required as far as I can tell)
That process generates an asset that you will then import back into Maya via "Cache / Alembic Cache / Import Alembic"

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Here you can see the export, simply select it and hit Import
This asset will now appear in the Outliner, it's a group with a BUNCH of curves representing one for each guide.
Reduce guide density to reduce curve density
To make this new asset usable we need to run the following script on it in order to add the proper RiCurves attribute
Again here is an icon for your Maya shelf.

- CombineGuideCurves_AddATTR_Export_Alembic.png (4.11 KiB) Viewed 3415 times
string $array[] = `ls -sl`;
for ($item in $array)
{
addAttr -ln "riCurves" -at bool -dv 1;
AlembicExportSelection;
};
Now save this new Alembic, it's the one we will use in Clarisse as a base for interpolation
Now in Clarisse, we have the same scalp geo, and I am using it as a geometry base on which
to scatter 100,000 points. The rough amount of human hairs on a human head.
using File / Reference / File to import the RiCurves combined curve asset we just exported from Maya
And now you you can see our curves in Clarisse ready to be used as guides in the interpolate node
Create an Interpolate node, using the Point Cloud as Geometry Support, and using the imported Curve Alembic as the Guides
And then you can see 100,000 hairs, ready for shading in Clarisse.
In the compressed file you will find Maya scenes to see my Xgen hair setup, a Clarisse PLE scene so anyone can look at the Clarisse setup and finally of course all the assets used above in terms of import export. Perhaps there is a way to combine some of the processes, but as of today I can't currently.

Hope this helps!