UPDATE(23 Jul 2013)
1. Service to Parkside Intermediate is not dropped and will continue on the 140. Service to Terra Nova in Pacifica is being moved to new route 49.

2. Route 141 will be altered on 26 Jan 2014. According to SamTrans summary of 26 Jan 2014 changes: “Realign route via San Bruno Avenue to improve direct service to San Bruno BART; only serve San Mateo Avenue on select trips.” Both the 140/141 will serve the new Caltrain station at San Bruno Ave.

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SamTrans has announced important changes beginning 11 Aug 2013. Here is a quick summary:

1. Routes 390/391 weekday service service eliminated and replaced by route ECR. Weekday ECR will run every 15 minutes between Palo Alto and Daly City BART stations. Service to San Bruno and South San Francisco BART stations discontinued.

2. Another change to Route 140 (Pacifica to San Bruno BART). The twice daily school bus trips are being discontinued and new Route 49 will do this service.

Changes scheduled 26 Jan 2014
1. Route 140 will be extended to SF Airport Airtran.
2. Express route KX will operate between Redwood City and San Bruno BART including an SFO airport. Peak hour service to San Francisco Transbay Terminal.

My take:
As noted in a previous post, the new ECR drops San Bruno BART dropping direct service to Tanforan and BART. People taking SamTrans have two choices taking the bus to Tanforan. Option 1: Take ECR to bus stop at Sneath & El Camino Ave(north and south) and walk to Tanforan. Option 2: Get off at San Bruno Ave & El Camino(north and south) and catch an eastbound 140 to San Bruno BART. BART is the easiest option. Simply take BART to San Bruno and you are right behind Tanforan. Downside: costs more than SamTrans.

There is also in 2014 another option of taking the KX. This mixed route is being shortened from its present start in Stanford to Redwood City. This shortened route will run between Redwood City and San Bruno BART during offpeak hours and into San Francisco during peak hours weekdays. A stop at San Francisco International is part of this route. Weekend service will operate hourly. Note: This route does not duplicate ECR and only stops at selected stops.

The 140 change is a surprise and threads a tough needle. SamTrans states it is forbidden by federal law from providing dedicated bus service to schools. That is why bus routes such as 140 divert over at certain times during the school year to serve schools like Parkside Intermediate. Now they are discontinuing such service and shifting the service over to a new route (49) in August. Presumably this limited run meets federal regulations by making all regular and school stops when it runs. One possible reason for this change is that commuters who boarded the school trip buses found it added extra time getting to BART or catching an ECR.

Source: SamTrans Transit Updates