That's a good question. But, no. Photoshop will open the file as a CMYK file conversion. What should happen is Photoshop honors the Spot Color channels established in Ai; in that scenarion you'd get your typical CMYK color channels and then additional color channels for the Spot Colors. That's too much work for a software application. But, I have to be honest. I've never Exported a Spot Color file out of Ai and into PS. I'm thinking you have to do it manually, perhaps creating a file for each Pantone color and then adding them into PS as additional Spot channels.