Is BSIM4 model implemented in cadence is anyhow different from the official one specified by BSIM group?
This derives from comparing a verilog-a model released from another company also implementing BSIM4 also against the cadence one and the results are somehow different.
For example parameters like PUA,PUB,WUB,WUC are not listed in BSIM4 2010 version manual but they appear on spectre manual. Usually for a model card (umc 90 for example) these are listed under other parameters.
This is a failing of the veriloga model you're using and the BSIM4 manual. If you look at the code from the bsim site:
It contains a definition of these parameters. So they're in the BSIM groups source code...
There are potentialy a few deviations from the official code, usually to add some additional features requested by specific customers (primarily a certain large foundry), but those wouldn't alter the default behaviour of the model unless those specific parameters/values were used ("spectre -h bsim4" lists these and makes it fairly clear they are specific to a particular foundry). But overall, there should be very good correlation with the BSIM group's code.