Each bus in the fleet is going to be having crank case ventilation systems installed.
Here's a little run down of what these do:
"Unlike exhaust emissions, crankcase gases normally escape into the environment through the crankcase vent tube. The ECS CCV system does the following:
A truly closed CCV system which effectively eliminates 100% of crankcase emissions at all times
Improves passenger compartment air quality, which is especially important in all types of buses (school, shuttle, urban, etc.), refuse and municipal fleets
Improves air quality for personnel working in the vicinity of an operating piece of equipment
Reduces fouling in the engine compartment and of charge air coolers, radiators, etc. increasing their efficiency" 
Personal, leased or 2007+ buses are exempt from the upgrades. P bus owners may pay to have job done, and I highly suggest it.
Here is the rundown on when these are going to be done. Each bus will take approximately half a day to complete.
Date: Bus Number: Take Bus Number:4/27 10402 187024/27 10401 18701------------------------------------------------------------
4/28 19903 18501
4/28 19902 18701------------------------------------------------------------
4/29 19901 18701
4/29 S19801 S10701------------------------------------------------------------
4/30 19701 18501
4/30 19402 18701------------------------------------------------------------
5/01 19301 18501
5/01 19202 18701------------------------------------------------------------
5/04 19201 18701
5/04 19001 18501------------------------------------------------------------
5/05 18702 n/a DELAYED UNTIL THURSDAY5/05 18501 n/a------------------------------------------------------------
5/06 18701 n/a