Enabling PLAR (Hotline feature) on Cisco 79x1 Phones

I am looking to set up paging/intercom with auto-answer on Cisco 79x1 phones using Asterisk 11.0.1 (patched with Gareth’s BLF code), and I would like to create an auto-dial line button.

The only way to enable auto-answer on Cisco 79x1 phones is to enable it for the entire line. If you do this on the phone’s primary line, every call is auto-answered, which is obviously not a solution. The workaround (here, here) for this problem seems to be to create a second line used only for intercom/paging. Having done this, I would now like to find a constructive use for this “lost” button. I would like to have the intercom line be used as a “hotline” to automatically dial the default paging group; when you pick up the intercom line, it automatically rings the other intercoms in the office. I’ve hit upon PLAR (private line auto ringdown) as the feature I’m trying to enable. Essentially, when the line goes off-hook, it automatically dials a preconfigured number (the number of the default paging group).

According to Cisco’s documentation for enabling PLAR on SIP, I simply need to use their Call Manager software to enable a separate dialplan for the line in question. Every example of an SEPxxx.XML file I can find for the 79x1 phones only has a single default for the entire phone. Trying to move that into a specific line does not work.

Does anyone know how to configure a unique dialplan/dialtemplate for each line on a Cisco 79x1 phone?

Thanks in advance.