See the following: http://www.gnupg.org/faq/GnuPG-FAQ.h...tible-with-pgp
Generally speaking, they should be compatible. However, being closed source, proprietary system, Symantec is free to commit all sorts of sins, including breaking compatibility with standards and charging for the feature. One thing to remember regarding public key encryption - the file must be encrypted with YOUR public key
in order for YOU to be able to decrypt it.