The (somewhat cumbersome) workaround I use is:
1. Export the calendar to a text file, Calendar Archive format: 1-Date, 2-Start Time, 3-End Time, 4-Title, 5 through 10-none.

2. Import to Palm Desktop (free download).

3. Export as vCal file

4. Import to iCal

5. Plug in iPhone

Hope this helps.