Dail Tone detection / Legacy PBX

I’ve been reading threads about connecting a Legacy PBX to an Asterisk box and have a couple of questions.

This is my intended setup: Legacy Lucent/Avaya Partner ACS phone system with TDM400 in Asterisk box connected as analog extension. The Extension that the Asterisk box is connected to will be configured to connect the “intercom” line first so calls coming in to the Asterisk box will be able to dial Legacy extensions.

The question I have is that in the above configuration the Legacy PBX sends a single tone on the Intercom extension rather than a standard dial tone. Will this confuse the TDM400 or Asterisk so that it will be unable to dial on that line? Is there a way to compensate?

Also, with the above configuration a call coming in to the Asterisk box from a VOIP extension would need to dial 9 to get an outside line after being transferred to the Legacy PBX, and there is sometimes a slight (1 sec or less) delay before the outside line picks up. Is there for me to insert a pause into a dial command or do I need a more complicated dialplan?