Yes, there are quite a few FOs who have been captains in previous airlines. Most, I would say, have been regional captains on aircraft such as the CRJ but there are some who were captains for major airlines on larger aircraft. As the rules changed for DECs to have a JCAB ATPL (it didn't use to be the case), there are many pilots who have the flying time and experience as a captain but no Japanese licence.
There are some who tell you within a few seconds how they were a captain on an XYZ but most of them just do the job and wait their turn for an upgrade.