When a site uses an ampersand in its title, xsl-portal often renders it as "&" which displays as "&".
Using the "?xsltUseTemplate=xml" query string to get the raw XML it seems that the over-escaping is coming from the XML itself, eg the pageTitle element includes the double-escaped ampersand.
Ampersands are double-escaped in the HTML title element, the main site header, and in quicklink-bar links to other sites. However, it is rendered correctly in the title of the current site when it appears (unlinked) in the quicklink bar.
The ampersand is stored in the database as a literal ampersand. The default portal (/portal) renders it correctly, as does osp-portal.