Triggering Publisher tasks from outside of QlikView is in a QlikView world called EDX - Event-Driven Execution". Depending on what version of QlikView Server you are using, the methods of triggering them differs, but it can certainly be done via HTTP POST commands in at least 9 and 10, even though 10> prefers via QMS API.
You can read about EDX in the documentation for QlikView Server.
1. In the foundations, the calls are in XML, yes, but in different shape. In 8.50 and 9, it's HTTP POST that sends XML. In 10 and upcoming 11, it's HTTP POST as legacy and within the QMS API as web services; that also sends XML in the end.
2. You can use the HTTP POST method from any language that can send HTTP requests. VBScript, C++, C#, VB.NET, Java, Python.. you name it.
3. Samples should be in the Reference Manual. Also check the QlikView Server SDK, that you find as addition in the QVS installation package.