The hot side oil seal on the turbine shaft is simply a piston ring seal, 2 of them typically. From my experience, they will leak SOME oil upon start up. In order for them to really seal up, a carbon dam is formed around these rings, behind the turbine wheel. If oil is getting backed up in the center section, it will leak, most of the time it will leak into the compressor side, since there is a low pressure area behind the comp wheel. I dont know exactly where your oil is coming from, but unless that turbo has been run for a while at operating temperatures, the carbon dam may not have formed yet. I'd probably run it under load for a while, and see if it seals up, if indeed it is a leaky turbo... Just my $.02
I just re-read, check that you dont have positive pressure in the crank case. if you are running positive pressure in the base, you could have pressure in the center section of the turbo inhibiting drainback, contributing to the leak.