Yes, if the file format is one that is accepted by MMM, like .ogg or .wav. However, they probably cannot be used the way that the Soundpool loops are used, unless they are structured similarly. They have to come with the BPM embedded in the file and pitch number, as far as I can tell, is a digit in the filename. How it gets the key, I don't know, probably embedded as well.
You can simply use the File Browser in the Media Pool to import the files.