I almost wrote off the idea that this was even remotely possible until I looked into it more on msdn and found an example.

/// <reference name "Ajax.js" assembly="System.Web.Extensions, ..." /> 

After doctoring it for my own script and assembly it was not working after trying several different renditions and wondering if it would ever work with the missing = in the name attribute and what the hell the ... was, I finally came to something that worked. 

/// <reference name="AjaxSnippets.SnippetManager.js" assembly="AjaxSnippets" />

SnippetManager.js is the file in my AjaxSnippets.dll.

The only snag is that I have not been able to get it to work in a script block inside an aspx page, but it does work in a js file.