db:

asterisk=# select * from ast_config where category = 'outbound-fallback';
  id  | cat_metric | var_metric | commented |    filename     |     category      | var_name |                     var_val
------+------------+------------+-----------+-----------------+-------------------+----------+--------------------------------------------------
 4388 |         29 |          0 |         0 | extensions.conf | outbound-fallback | exten    | _1NXXNXXXXXX,1,Dial(IAX2/user@trunk-us/${EXTEN})
 4389 |         29 |          0 |         0 | extensions.conf | outbound-fallback | exten    | _44Z.,1,Dial(IAX2/user@trunk-uk/0${EXTEN:2})
 4392 |         29 |          0 |         0 | extensions.conf | outbound-fallback | exten    | _XXX.,1,Dial(Zap/g1/00${EXTEN})
(3 rows)
mysql extensions reload:

   -- Registered extension context 'outbound-fallback'
   -- Added extension '_44Z.' priority 1 to outbound-fallback
   -- Added extension '_XXX.' priority 1 to outbound-fallback
   -- Registered extension context 'inbound-did'
a couple of lines later with other extensions:
   Aug 21 22:11:20 WARNING[376855]: pbx.c:2882 ast_context_create: Tried to register context 'outbound-fallback', already in use

extensions reload:

    -- Registered extension context 'outbound-fallback'
    -- Added extension '_1NXXNXXXXXX' priority 1 to outbound-fallback
    -- Added extension '_44Z.' priority 1 to outbound-fallback
    -- Added extension '_XXX.' priority 1 to outbound-fallback

show dialplan:

[ Context 'outbound-fallback' created by 'pbx_config' ]
  '_1NXXNXXXXXX' => 1. Dial(IAX2/user@trunk-us/${EXTEN})          [pbx_config]
  '_44Z.' =>        1. Dial(IAX2/user@trunk-uk/0${EXTEN:2})       [pbx_config]
  '_XXX.' =>        1. Dial(Zap/g1/00${EXTEN})                    [pbx_config]