Looking at the legal definitions of evasion and obstruction, I don't see anything that applies, especially considering the typical use cases. Obstruction charges usually stem from providing false testimony or evidence, tampering with evidence, or witness tampering.

Evasion - for Portland, they haven't been formally approved from what I read. Doesn't necessarily mean that because they aren't formally approved that the actions are illegal. But I also see that Portland passed a law in Dec 2015 to allow Uber and Lyft on a permanent basis under existing transportation laws that would require them to provide trip data to the city, conduct background checks, etc.

Trying to avoid contact in the course of an investigation or other formal proceedings is generally not illegal. Think about process servers trying to serve papers like subpoena's, decrees, or other court documents on behalf of the state. It's not illegal to avoid those people and try to hide from them. You don't get obstruction or evasion charges even if you are fully aware they are trying to serve you and make efforts to avoid them.