The following Modern Medicine article has the most specific information that I have found about the latest studies. These consist of meta-analysis, meaning several individual studies were taken together and analysed, giving more powerful estimates of the true effect size than those derived in a single study.

From that page you can also follow links to abstracts of the original studies:

Public Smoking Bans Linked to Fewer Heart Attacks

TUESDAY, Sept. 22 (HealthDay News) -- Bans on smoking in public are associated with a drop in hospitalizations for heart attacks and the benefits increase with time, according to one study in the Sept. 29 Journal of the American College of Cardiology and a second study published online Sept. 21 in Circulation.

In the Journal of the American College of Cardiology, David G. Meyers, M.D., and colleagues from the University of Kansas School of Medicine in Kansas City performed a meta-analysis of 11 reports examining the effect of public smoking bans on acute myocardial infarction hospitalizations in 10 locations in the United States, Canada, and Europe. They found that the risk of acute myocardial infarction fell by 17 percent overall, but fell by 26 percent each year after implementing the ban.

In Circulation, James M. Lightwood, Ph.D., and Stanton Glantz, Ph.D., from the University of California in San Francisco performed a meta-analysis of studies examining the effect of public smoking bans on acute myocardial infarction hospitalizations in 12 locations in the United States, Canada and Europe, and compared the observed data with a mathematical model of individual risk based on exposure to passive smoke. They found that one year after the law was implemented the pooled random effects estimate of the rate of acute myocardial infarction hospitalization was 0.83 and the benefit continues with time.

"A 17 percent risk reduction for acute myocardial infarction is not trivial," writes the author a an editorial accompanying Meyers' study. "Therefore, cardiologists should expand their clinical repertoire to include screening and counseling for secondhand smoke exposure, just as they screen for lipid disorders."