Yes, the digit map syntax is called a "hotline" and you'd want it to work without delay. Here are a few examples from the Admin Guide:
<:1234> – Matches an empty phone number and replaces with 1234. This is the syntax for a hotline to 1234
<S0:1234> – Equivalent to the last example
<:#> – Hotline to the number #
<S0:#> – Equivalent to the last example
<S4:1234> – Call 1234 if no digits entered for 4s. This is the syntax of a warm line.
I played around with these in the past (sort of as an experiment), and they work as described. You put the above rule(s) in the digitmap of the phone port, on an Obi202 that is Physical Interfaces > Phone x Port > PHONE Port > Digit Map. Don't have an Obi110 to tell you the exact field hierarchy.
If I recall this correctly, you want the example starting with prefix S0 -- S-Zero, which places the call as soon as the handset is picked up, you don't have to press any keys.