Wikipedia (questionable source) and www.utahrails.net (much more reliable source, backs up Wikipedia.)
Portland Traction Company's corporate record can be found here:
[
egov.sos.state.or.us]
The Missouri Pacific note is in UP's 2009 Annual Report:
[
www.up.com]
Looks like UP has filed to dissolve PTC, the filing was on 09/26/08 but the business name is still active.