You cannot get tick data using Tradestation as a data feed. I know you can load tick charts on the Tradestation platform so it seems strange.
Here is the answer I received from support when I asked this same question: Not the best news, but at least it is an answer
"The Tradestation API does not support historical ticks in the feed therefore tick charts are not available via MotiveWave.
The lowest time interval supported historically would be based on seconds."