One possibility is to use partIO (https://www.disneyanimation.com/technology/partio.html). You can convert from/to various particle and point cloud formats. PDC (the caching format of Maya's legacy particles) is one of the available formats.
I used it to convert xyz data into PDC, which I attached to an existing particle object. To be able to convert the point cloud to a mesh, you need nParticles. For this I created a nParticle object with the same number of particles as the legacy particle object and set the legacy particles as the goal for the nParticles.
I think you should also be able to get the point cloud into Maya with SOuP (http://www.soup-dev.com), though I do not have real experience with this.
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