As you will note, I am using '&' instead of '&', e.g. at ...../poso&search.....
When I run this in the StylusStudio debugger, I get no meaningful return value. Instead I get like 'Invalid input' when I inspect the variable varPOLineKeys.
When I use a web browser, I use the following URL:
Subject:& and & in web service call Author:Soren Hojbjerg Date:18 Jul 2013 07:53 AM
I am using Saxon 9.4.0.6. It makes no difference if I check on warnings (-w1). The xslt runs, but I get a return xml like <error>Invalid input</error>.
Perhaps I should construct an example using a web service available on the internet. This will take me a day or two. I will get back.