The new hires come as nationwide infrastructure needs keep growing and as several firms have left or scaled back their muni efforts.
The tax could result in an increase in demand for the state's municipal bonds.
The review, which included mostly Texas and Colorado bond issuers, comes as the amount of voter-approved debt authorized for districts is exploding.
This strength comes after another "challenging week" for the muni market, which continued to deal with ongoing macroeconomic uncertainty and somewhat heavy supply, said Daryl Clements, a muni portfolio manager at AllianceBernstein.
Bernardi Securities founder Edward Bernardi passed away peacefully on March 21 in his Lake Forest, Illinois, home. He was 95.
S&P cited the system's structural challenges, physical risk exposure and uncertainty about the system's overall financial and operational trajectory.
