The ODP or SID is not intended for OEI terrain and obstacle clearance since the criteria does not consider both the actual takeoff flight path of the aircraft following an engine failure nor does the climb gradient on an ODP or SD account for all obstacles that much cleared to meet the operating rules. An ODP or SID provides obstacle clearance with all-engines-operating because that's what its criteria assumes. Make sense?
With the proper obstacle information concerning obstacle height above the runway and distance from reference zero, the FMS calculator can be used to calculate OEI takeoff obstacle clearance in accordance with the operating rules. Here's an important caveat. You need the relevant terrain & obstacle data and collecting that data no small feat. There are multiple data sources that need to be consulted, which is why the airlines have performance engineering departments dedicated to that task. For the business aviation community, we have contract providers such Aircraft Performance Group, ASAP Inc., Aerodata (now owned by Garmin), and Jeppesen OpsData through ForeFlight that provide this type of engineering support, and provide takeoff performance/obstacle clearance data in the form of airport runway analysis.
As real CL300/350 pilot, I would never attempt to gather the obstacle data from the various sources and use the FMS calculator, in the same way that I would never attempt collect obstacle data and build my own instrument approach procedure to a runway. The FAA is expert in building instrument flight procedures and these performance engineer providers are the experts in airplane performance and engine failure escape procedures.
I was never really quite sure why the FMS manufacturers (OEMs) put the obstacle clearance routine in their FMS. It's not unique to Collins. It's in the Garmin 5000 as well. If you had one known obstacle that you wanted to clear, one that as not accounted for in your contractor-provided analysis, for example a temporary obstacle, then yes, I could see a use for it. Although in 18 years of flying Collins FMS equipped aircraft, I have never used it other than for experimentation and familiarization.
Rich