Hi Zak and Dick,
The login page for courses is generated by Login.pm, and Login.pm does not use WeBWorK::PG, so does not have access to all of the pg code.
The content generator modules "inside" of webwork are subclasses of ContentGenerator.pm, and that's how they get WeBWorK::PG. I just quickly looked at this to answer your question, and I don't know how easy it would be to add this capability to Login.pm. I'm sure there was a reason it was done this way; perhaps there are permissions/security issues behind it.
Edit: On the other hand, you do get the $ce object in Login.pm, and that has a ton of information in it, and you can add to it in course.conf. So, you could edit Login.pm to get access to the information you want through $ce and then display that information somewhere on the page. You woudn't be able to do it through course_info.txt or using pg macros, but it might be an easy way to accomplish what you want to do.
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