Returns inside text objects appear to be stripped out when saved as PICT and reopened into another application. When reopened, the text objects will be the correct size.
However, if you make the text object wider, the text will reflow to fit the new bounding box, as if no returns were entered into the text object. When tested with MacDraw Pro, ClarisWorks and Canvas, the issue seems to occur going from any one program to any other. So, it doesn't seem to be an application-specific issue.