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The CASA task simalma works in CASA version 4.2. We expect to release 4.2 in November 2013.
You can find a CASA guide for using simalma here: Simalma_(CASA_4.2)
You can find a guide specific to simulating ALMA data here: Guide_To_Simulating_ALMA_Data
You can find a guide to simulating interferometric data in CASA version 4.2 here: Simulating_Observations_in_CASA_4.2
You can find a guide to simulating interferometric data in CASA version 4.1 here: Simulating_Observations_in_CASA_4.1