IIRC for Gen4 Outbacks (2010-2013) you can disable the alarm with the following procedure:
1. All doors closed, turn key to "On"
2. Hold down driver's door "lock" (towards the rear) button for 1 second
3. Open driver's door (while continuing to hold the lock button)
4. Continue to hold driver's door "lock" button for 10 seconds
5. Alarm system on/off will be confirmed by the horn honking (once for alarm system on, twice for alarm system off)
Repeat the process to change back alarm system to on or off. The steps are in the owner's manual..I think the above is correct.