On a user's desk phone, a call shows up as "315554443333" with 3 being the dial-out code.  This way, a user can easily return a missed/received call.  In Lync, the call shows up as "+5554443333".

This is fine for Lync users, but if a Lync user were to transfer a call to a desk phone user, the call appears as "+5554443333".  The desk phone user can no longer return this call, they would have to dial the digits manually.

How would I go about re-translating this number?  T

From My understanding this by design 

However you can try change the calling number in the trunk configuration 

http://blogs.msdn.com/b/microsoft_press/archive/2013/03/25/from-the-mvps-using-lync-server-2013-calling-number-translation-rules-to-change-display-number.aspx

Thank you for the link, but unfortunately we are still running Lync Server 2010 and Calling Number Translation rules are not available.  We want incoming calls to Lync phones to show the +number, but when we forward from a Lync phone to a desk phone, we want to drop the + and add "

Hi,

What are your desk phones? Are they Lync registered devices, or part of a separate PBX solution with Lync interoperability?

Ah, I did not include that in the original post, sorry.  We are using a CUCM with a SIP trunk for Lync, and our desk phones are 7961's.  We are working on integrating Lync, but need to address this call forwarding issue.

Thanks, and to be clear, your PSTN connection is on the Cisco Call Manager with a SIP trunk off to Lync? If this is the case then the only possible point you would be able to achieve this is with source number digit manipulation inbound on the CUCM side, but I'm not sure if this is possible due to limited knowledge of that system - someone here might know.

Or is there a gateway / SBC that both systems are connected to? If this is the case, such as an AudioCodes or Sonus appliance, then you can manipulate the number on its way through. Although it sounds like you have the former scenario.

That is correct, PSTN to Call Manager with SIP trunk off to Lync.  I am thinking the manipulation needs to occur in Lync, not in Call Manager.  We are using several number translations already, here is an example:

OutsideCaller at 555-444-3333 calls InsideUser1 at 222-333-4444.  The user has a desk phone and is configured for Enterprise Voice in Lync, so both their DeskPhone1 extension (4444) and their LyncPhone extension (3444) ring.  315554443333 appears as the Calling Number on DeskPhone1, but +5554443333 appears on LyncPhone.

1.  If InsideUser1 forwards a call received on DeskPhone1 from OutsideCaller to InsideUser2 who answers it on their DeskPhone2, it appears on DeskPhone2 as 315554443333 (GOOD).

2.  If InsideUser1 forwards a call received on DeskPhone1 from OutsideCaller to InsideUser2 who answers it on their LyncPhone2, it appears on LyncPhone2 as 4444 (BAD, should show original calling party 315554443333).

3.  If InsideUser1 forwards a call received on LyncPhone1 from OutsideCaller to InsideUser2 who answers it on their DeskPhone2, it shows on DeskPhone2 as +555444333 (BAD, should display number as 315554443333).

4.  If InsideUser1 forwards a call received on LyncPhone1 from OutsideCaller to InsideUser2 who answers it on their LyncPhone2, it shows on LyncPhone2 as +555444333 (GOOD).

I hope this helps to clarify.

We seem to have solved this problem for now.  We created a Calling Party Translation Pattern in CUCM for the Lync partition that removes the + and appends 31.