I am pretty sure only Challengers aver made it through those curves as well. The wheelbase for 4 - 80 inch drivers is pretty damn long.
Video link: 1995-10-25 UP3985 at East Portland
A few years prior in 1993 the SP and SJ engineering team travelling with the X2000 deemed those curves too tight of radius to allow the demonstration train to use it as a wye as well.
The gal in the video was from KXL and recorded the audio to play on the air later in the day.