Agilent ADS has not included the source S2P files for devices with s-parameter models for well over 10 years I believe. Instead the data is packaged in a set library files that are used during simulation of such devices. So to that end there doesn't appear to be any way to simply browse to or read this data.
For the ATF-34143 device specifically though all may not be lost. Hewlett-Packard/Agilent/Avago have always distributed a datasheet for this device that contains s-parameter data including the necessary noise parameters.
ATF-34143 SC-70 (SOT-343) Low Noise 31.5 dBm OIP3
This data does not appear to have change now for many years. The data that you show from the MWO entry for the device matches exactly the data from the datasheet for one of those published bias points, Vds 3V @ Id 20mA. So one has to suspect that MWO is simply reusing the manufacturer's measured data off that datasheet. It is also possible from the above link to download actual s-parameter datafiles from Avago including:
**broken link removed**
Which also exactly matches the MWO data.
One important piece of reference information from both these sources is the second comment line in the datafile which shows it to be "LAST UPDATED 01-29-99". This data is over 14 years old.
Now if we look at the devices in the ADS Component Library list you will see that there are five different variants of the data for Vds=2V Id=20mA, Vds=3V Id=20mA, Vds=3V Id=40mA, Vds=4V Id=40mA and Vds=4V Id=60mA. Exactly the same bias points as are available as s-parameter data to download from the Avago website. More importantly though the components all include the suffix in their name of "_19990129". This is the date of that data and it exactly matches the "Last Updated" date in the s-parameter files from Avago and MWO. Too much of a coincidence. So I would say that ADS is also using exactly the same s-parameter data as is still published by Avago and also available in MWO.
See also <ADS Installation Dir>/ComponentLibs/models/sp_hp99.library and find the lines immediately following the first match for "sp_hp_ATF-34143_3_19990129".