It happens that simulations cannot start because of errors found by spectre in 'multibit_pcell' during hierarchy flattening. The typical error message reads: ERROR (SFE-1997): "input.scs" line#: IABC.V0: parameter `dc': Cannot run the simulation because parameter 'a0' has been used but no value has been assigned to it.
I have discovered this issue can be solved in a test editor respectively in an ADE-L session, by manually launching "Recreate Netlist". But then, how can netlist recreating automatically be forced before any test simulation in ADE-XL?