Does Windows or Linux have any tools for accessing a FileVault2 encrypted drive's contents?
On Linux, the libfvde project aims to support decoding FileVault2. Yogesh Khatri wrote an overview article where he suggests starting with libfvde's wiki.

On Windows, the company Passware claim support for decrypting FileVault2 drives as part of Passware Kit Forensic 13.1. A CNet article mentions the software and highlights the feature in an included screenshot: