This table says it's a French introduction from the 1970s. Notice all the other "repeat bloomers" on the same page.

Here is a link that might be useful: Late Lilacs

Planted a Josee spring 2007 (from mail order). Just existed all summer until Sept. when it grew some and had 1 blossom. Survived winter (very snowy Wisconsin) and is thriving now and has many blossoms right now. Nice fragrance. Should I dead head to encourage repeat bloom?