This wasn't easy to find. CBO must think these reports are top secret. They made it hard as hell to copy too.
http://www.cbo.gov/ftpdocs/107xx/doc10781/11-30-Premiums.pdf Employment-Based Coverage
The legislation would have much smaller effects on premiums for employment-based coverage, which would account for about five-sixths of the total health insurance market. In the small group market, which is defined in this analysis as consisting of employers with 50 or fewer workers, CBO and JCT estimate that the change in the average premium per person resulting from the legislation could range from an increase of 1 percent to a reduction of 2 percent in 2016 (relative to current law).6
In the large group market, which is defined here as consisting of employers with more than 50 workers,the legislation would yield an average premium per person that is zero to 3 percent lower in 2016 (relative to current law). Those overall effects reflect the net impact of many relatively small changes, some of which would tend to increase premiums and some of which would tend to reduce them (as shown in Table 1).7