Below is an article with somewhat different numbers.
Called Wheatridge Renewable Energy Facilities, it comprises 300MW of wind power, 50MW of solar PV generation and a 30MW battery energy storage system (BESS) with four-hour duration (120MWh).
Instead of 275 MW from the batteries, it is only 30 MW. (About 5% of the coal plant capacity referred to in the OP). But, instead of 26 minutes of duration, it is a more respectable 4 hours.
Also, it looks like the state of Oregon is a net exporter of electricity. This is largely due to the hydro resources they have available along the Columbia River, and other locations. Therefore, they may not need to burn more natural gas to replace the coal plant. They just might not export as much power to California, for instance.
- Pete