Under version 2.5, you had to save the file on both platforms as TIFF files or EPS files. See also the paragraph on the signature of those files and how to get correct EPSF signatures even for the color seps. Importing Freehand EPS files Photoshop can't rasterize the ESP files produced by Freehand. In this case, the program uses the low-resolution preview picture.
Results are of course bad.
The solution is to export the file as an Illustrator 3 format. The file is then properly rasterized in Photoshop. All trademarks acknowledged.