I am trying to call $this->getIsAnchor() from a category template file to show certain information if the category has layered navigation. The function is always returning false, even when it should be true.
Is there a problem with calling the function from a template file this way? If so, what is the proper way to call this function?
You need to make this call against the category instead:
$_category->getIsAnchor();
Depending on what you are trying to achieve, you may find using layout.xml a cleaner option. There are different handles for layered and non layered categories:
Non Layered Categroy Handle
<catalog_category_default>
Layered Category Handle
<catalog_category_layered>