Confirmed that the issue doesn't seem to affect heat CLI.
While Congress is encountering authentication errors accessing heat, I could use the heat CLI to access heat information without issue. (e.g., $ heat config-list).

Also, here are the corresponding logs between Congress showing error authenticating and h-api showing failed authentication token.

Congress:
2016-03-18 16:55:17.516 ERROR congress.datasources.datasource_driver [-] Datasource driver raised exception
2016-03-18 16:55:17.516 TRACE congress.datasources.datasource_driver HTTPUnauthorized: ERROR: Authentication failed: Authentication required
2016-03-18 16:55:27.546 ERROR congress.datasources.datasource_driver [-] Datasource driver raised exception
2016-03-18 16:55:27.546 TRACE congress.datasources.datasource_driver HTTPUnauthorized: ERROR: Authentication failed: Authentication required
2016-03-18 16:55:37.582 ERROR congress.datasources.datasource_driver [-] Datasource driver raised exception
2016-03-18 16:55:37.582 TRACE congress.datasources.datasource_driver HTTPUnauthorized: ERROR: Authentication failed: Authentication required

h-api:
2016-03-18 16:55:07.478 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:07.478 WARNING keystonemiddleware.auth_token [-] Identity response: {"error": {"message": "Could not find token: a8a3a526ca5f49a4b2572cc49a0f6c2f", "code": 404, "title": "Not Found"}}
2016-03-18 16:55:07.479 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:17.514 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:17.514 WARNING keystonemiddleware.auth_token [-] Identity response: {"error": {"message": "Could not find token: a8a3a526ca5f49a4b2572cc49a0f6c2f", "code": 404, "title": "Not Found"}}
2016-03-18 16:55:17.515 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:27.543 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:27.543 WARNING keystonemiddleware.auth_token [-] Identity response: {"error": {"message": "Could not find token: a8a3a526ca5f49a4b2572cc49a0f6c2f", "code": 404, "title": "Not Found"}}
2016-03-18 16:55:27.544 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:37.577 WARNING keystonemiddleware.auth_token [-] Authorization failed for token
2016-03-18 16:55:37.578 WARNING keystonemiddleware.auth_token [-] Identity response: {"error": {"message": "Could not find token: a8a3a526ca5f49a4b2572cc49a0f6c2f", "code": 404, "title": "Not Found"}}
2016-03-18 16:55:37.578 WARNING keystonemiddleware.auth_token [-] Authorization failed for token