There are a couple of reasons you didn't see any Tesla semis on that route. Big fleet operators are the only ones who are running them right now. Pepsi has a small fleet that is currently also participating in the Run on Less trial (depot). WalMart is salivating to get some also because their bean-counters see massive cost savings for their most of their uses.
Secondly, there is not currently charging infrastructure that will support them. Tesla is using their fleet to transport their products between Reno, NV and Fremont, CA and a couple of their other facilities so you will not see any outside of those routes right now. Tesla is working on chargers for the trucks, between CA and their facility in TX. They are finding that power requirements are huge and they need a dedicated utility service, seperate from the plants they are servicing. I expect to see one or two of their grid scale batteries at the depots, in order to keep peak demands reasonable. That will take a while but economics of an electric fleet will drive progress there. Just like the coveted Tesla Supercharger network, the Tesla truck charging network will take time to build out. The current goal for the Tesla Semi guys is to cater to the drayage market that makes up over 90% of the class 8 truck usage. No one has claimed the semis will replace the over-the road long haul fleet in the next ten years.
So, back to the Run on Less trial: It is over and the organizers are busy compiling results. All three of the Pepsi trucks that were in the trial were the 300 mile versions. Pepsi said they were hauling beverages but will need to wait to confirm that. On day 17 of the trial, truck 3 drove 1076 miles. 92.6% of the distance was covered at a speed of 50 MPH +. The truck started with a 95.19% charge and spent 11.1% of the 24 hour period charging or about two hours and 40 minutes in the 24 hour period. The trucks were limited to charging at Pepsi terminals equipped with electrical service capable of delivering current at the levels required. 
For my farm, I can certainly see where a semi would work. We don't put a ton of miles on every day and a significant portion of the time is spent with the truck only providing climate control. Our bin site has a modest 3-phase service that could provide 25 Kw of charging overnight. 10 hours on the charger would supply 250 Kwh. Test results look to be slightly less than 2 Kwh / mile driven, so that 10 hours would make for 120+ miles of travel every day. That would be plenty for our farm.