Hi Tim
NOTE:
Since posting this I now have a deeper appreciation of the difference between JUri::root(); and JPATH_ADMINISTRATOR and JPATH_BASE
Holy smoke, it is exactly this sort of thing that takes me a loooooong time to appreciate
END NOTE
Well, I have digested further what you have written.
Would you be willing to assist me further?
If no, fair enough, but if yes ->

To highlight where I m at today
I have created an access.xml file.
Placed it in:
JURI::root().'libraries/teachers-pet/base/access.xml';
I have my permissions in there ie...
<?xml version="1.0" encoding="utf-8" ?>
<access component="teachers_pet">
<section name="permissions">
<action name="core.create" etc....
Doing some tests, trying to see what's what I am trying to pull these permissions:
// TEST 1
// set path
$path = JURI::root().'libraries/teachers-pet/base/access.xml';
// get actions
$actionsFromFile = JAccess::getActionsFromFile($path,"access/section[@name='permissions']/");
// have a look at result
var_dump($actionsFromFile);
// result
bool(false)
// TEST 2
// set path
$path = JURI::root().'administrator/components/com_content/access.xml';
// get actions
$actionsFromFile = JAccess::getActionsFromFile($path,"/access/section[@name='article']/");
// have a look at result
var_dump($actionsFromFile);
// result
bool(false)
Jon