All mention of either using a symlink or data/index separate data directories state that MyISAM is the only supported (https://dev.mysql.com/doc/refman/5.5/en/symbolic-links.html). However, I found this bug report (http://bugs.mysql.com/bug.php?id=49808), that states "only supported for MyISAM and ARCHIVE tables". This also may be just for partitioning.
I believe just "testing" this is not an option, because the MySQL documentation mysteriously states "For files used by tables for other storage engines, you may get strange problems if you try to use symbolic links. "
Does the ARCHIVE storage engine support symlink or separate data directories?
UPDATE: Related question