You're using R11, which (unlike R12) allows report tables locked to no model objects, by copying and pasting a data table directly from Data tab to Reporting tab. These report tables can include metrics (model metrics or calculated metrics) if we use functions such as LookupObjectTotalValue or LookupObjectUnitValue - which might solve your need.
Or, you could adjust your View Filters (redaction applied to your Cost Source object) and your unit drivers to allow spend "B" back into your Cost Source object and yet still calculated separately (and even with separate view permissions).
For instance, if you currently have two Cost Source unit drivers of OpEx Fixed and OpEx Variable, consider instead having four unit drivers:
OpEx Fixed Spend A
OpEx Variable Spend A
OpEx Fixed Spend B
OpEx Variable Spend B
...which will allow us to separately report on these tagged metric values at any model object level, and will minimize report customizations needed.