Any pause in SIP dialling has to be doable from the device doing the dialling. While some analogue phones attached to an ATA are capable of this, most other devices usually aren't. The problem with inserting a pause is that there must be some way to tell the device to "send these digits, up to this point, now", then wait, and SIP doesn't work that way. All digits are sent as a complete package.
So, I'm thinking that the answer is going to be , no.