There shouldn't be any problem adding keys using Maxscript. For example, to add keyframes to the Start parameter for the first spline in the base objects list you could try the following:
with animate on
at time 0 $.bastart = 0
at time 25 $.bastart = 45
at time 75 $.bastart = 70
You'll see now that the keyframes are visible on the track bar and in the Curve editor as normal.