We faced similar issue.
The Apptio support group came up the workaround solution. They created ITP extract of Monthly Actual / Forecast data in TBM Studio. The extract is available in CT after each month-end close. We can then upload into ITP/Labor. Per my understanding, this is temporary solution. I am hoping they come up more streamline process.
If you want to learn more, I will be happy to share the workaround process steps documented in our runbook.
#ApptioPlanning(ITP/ITFMF)