I figured it out. Just in case anyone else is interested:
IP of BI:81/admin?camera=x&alerts=y.
where X = camera name.
and y = alert status required. Set y to one of the following values:
-1 = never
0 = when this camera is triggered
1 = any camera in group is triggered
2 = when any camera is triggered
FWIW, no authentication in the URL is required if BI user “anonymous” is enabled. But If user “anonymous” is NOT enabled and you have created a user and password in BI to be used when issuing the above HTTP command, then you must also place that user/password at the end of the URL that is sent to BI.
That would add “?user=username&pw=password” to the end, so the example URL now would be