I found a round by round description of the bout via the archives of the San Fran Call. Looks like they gave the bout to Hart by one round....by his winning the 20th and final round. Something like 7-6-7 in rounds.
The round by round description which is quite extensive indicates sheer aggression was the criteria that won the bout for Hart. Johnson out boxed him all the way but for some reason this was at least in part overshadowed by Harts aggressiveness. At the beginning of each round he would rush Johnson throwing punches. Hart never let up until the final bell.
Shorter article the day after the fight from all the LA Herald. http://chroniclingamerica.loc.gov/lccn/sn85042462/1905-03-29/ed-1/seq-10/
Johnson's own corner urged him to pick up the pace, but he did not, possibly because Hart's body punches took their toll. This was essentially viewed as a title elimination match to face Jeffries. Jeffries said he would take the winner. Afterwards, he said if the demand was there he would face Hart. Below are Johnson's own words: So it sounds like Johnson did in fact admit Hart defeated him on that day.
