You might post this query on the iPhoto forum and perhaps someone there can provide an answer.
I tried this on my MBP and it seems that you have to restore the entire iPhoto Library. What I did was put the current library in a separate folder on the desktop and then I restored the library from a prior date. If you were to do that, you then could extract the desired photos and then delete the restored library. Then place the current library back to the original location and import the desired photos.
Not tidy but it seems it will work.