Taoyuan Metro Corporation has made the following announcement in Chinese. My quick translation:

Test operation will commence on February 2. Testing hours will be 8AM to 4PM. The fare will be free during the 4 weeks of test operation. Only groups will be able to ride the metro during the first two weeks, and have to go through application process to be admitted. The third and fourth weeks of test operation will be open to the general public. Stations will distribute tags for free rides at 7:40, 9:40, 11:40 and 1:40 PM and is limited to 20,000 per day.

Standard operation will begin on March 2. Fare will be discounted by half for the first month. Standard fare will apply starting on April 2. The fare to/from Taipei Main Station will be NT$160.

The trains come in purple and blue colors. Purple trains are express and stops at Taoyuan Airport Terminal 1 & 2 (and the future Terminal 3), Chang Gun Memorial Hospital and Taipei Main Station. The express train will take about 35-36 minutes to reach the airport from Taipei Main Station. Blue trains are commuter (local) trains and stop at all stations, and take about 45 minutes between Taipei Main Station and the airport.

In the future there are plans to increase frequency from every 10 minutes to 6 minutes and increase capacity via additional cars.