Hi Martin,
As far as I know, according to DOCSIS Timing Interface Specification (CM-SP-DTI-I05-081209) there is a strong recommendation to use DTI Root and Slave server and also if they need to be located in different buildings (for instance) it is strongly recommended to use GPS or at least SONET/SDH network for syncronization between DTI servers.
Cisco IOS XR Release 3.9 introduces support for SyncE-capable Ethernet on the Cisco ASR 9000 Series Router.
But I'm not sure DTI Timimng protocol is the same as Sync-E so even if we can suppport Sync-E on ASR9K
http://www.cisco.com/en/US/partner/docs/routers/asr9000/software/asr9k_r4.2/interfaces/configuration/guide/hc42ethi.html#wp1012317
and tranposrt clocking over Ethernet links there is a question if DTI clients will be able to understand Sync-E
You may also ask uBR10K experts to verify if uBR10K DTI port is compartible with Sync-E and if Sync-E will be sufficient to "feed" DTP clent port on uBR10K with the clocking.
HTH
/vadim
P.S. As far as I see in the specification even the L1 specs are a little bit different for DTI UTP connection and standard Ethernet connection so I realy doubt DTI port will be able to "understand" Sync-E.