I had some time, so here is the solution. You need to use OBi Expert to make these configuration changes:
OBi1022
IP Phone -> Phone Settings -> DigitMap
The 1st rule is: [1-9]x?*(Mpli)
Change it to: [1-4]*xx.S3
Make sure you don't remove the beginning ( and the | after the rule
IP Phone -> Phone Settings -> OutboundCallRoute
The 1st rule is: {([1-9]x?*(Mpli)):pp}
Change it to: {(Mpstn)*(xx.):pp}
User Settings -> User defined Digit Maps -> UDDM2
Label: pstn
DigitMap: (<1:510111111>|<2:510222222>|<3:510333333>|<4:510444444>)
Replace 510111111 thru 510444444 with the OBi numbers of your OBi2xx's
Each OBi2xx
Voice Services -> OBiTalk Service -> InboundCallRoute:
{610123456>(xx.):li},{ph}
Replace 610123456 with the OBi number of your OBi1022
Dial 2*18005551212 to send the call to OBi2xx#2
Dial 3*18005551212 to send the call to OBi2xx#3
If I misunderstood you and you don't have OBiLine adapters and you want to route calls to an SIP provider on the OBi2xx's, just use the following OBiTalk OutboundCallRoute:
{610123456>(xx.):sp1},{ph}
This will route calls to SP1.