I heard that the two tunnels were bored out to standard gauge dimensions in the first decade of the 20th Century.
Alva Lyons once told me that another plan was to have the San Juan Extension take off from Del Norte or South Fork and go over Wolf Creek Pass to Pagosa Springs then rejoin the original line at Pagosa Junction. There would have been a Wolf Creek Pass Tunnel, several miles long.
However the Three Tunnels Measure failed to pass at the Colorado polls so there was no need to standard gauge the entire Fourth Division.