I haven't specifically used W3TC with WP 3.9 on HHVM, but HHVM does support APC and Memcached, so object cache backends that use those should work. I can confirm that my standalone APC object cache backend is working fine in HHVM.
Do note that there is currently a WordPress incompatibility in HHVM due to a bug in how HHVM sets cookies. You can log in to WordPress, but you won't get a cookie that is valid for the front-end of your site. So you won't see a toolbar. And there also seem to be issues logging out. I opened a bug report with HHVM here.