Pointing to other academic research, the authors said a combination of tax advantages and avoidance of PPACA penalties are working together to support the continuation of coverage — even among smaller firms that don't face the stringent regulations and sanctions that larger firms must confront.

"Abraham and coauthors [from the National Institute of Health Care Reform] estimate that employers of the vast majority of workers now offered employer-sponsored insurance will continue to have an economic incentive to offer coverage under the ACA," the researchers wrote.

"The largest firms will continue to have a strong incentive to do so because the large benefit of the employer coverage tax exclusion and penalties avoided by offering coverage greatly outweigh the value of the premium subsidies that workers would receive if their employers did not offer coverage. Firms with fewer than 50 workers will face significantly lower economic incentives to offer coverage because they employ a larger share of low-income workers and are not subject to the employer mandate. However, Abraham and coauthors estimate that most small firms that already offer coverage are likely to continue to do so."

Most earlier studies that have queried employers about their plans for continuing to offer coverage to the workforce have found a solid preference for doing so.

While offering coverage as a recruiting and retention strategy is usually cited as the main driver behind the strong trend found at major corporations, other factors may also be at work.

One may be a fear of offloading folks to the public exchanges before those exchanges have proven they could provide quality, affordable coverage.  A Towers Watson survey in September found that 99.5 percent of employers who participated in the survey said they would not move employees over to the public exchange system for health coverage, and three-quarters said they didn't think public exchanges would be a viable alternative for employee health insurance for at least the next two years.

Another factor could be the Internal Revenue Services' ruling last spring regarding employer payment plans. Essentially, under such a plan, an employer would set aside dollars to use to reimburse employees for coverage obtained from a public exchange. Some believed this arrangement would satisfy the guidelines for the employer's responsibility to provide coverage or pay a fine, as set out in the Patient Protection and Affordable Care Act. The IRS said such plans don't meet the guidelines and would result in substantial fines for employers.

Additionally, consultants have advised corporations that offloading workers to alternative insurance formats could deprive them of valuable health data about their workforce.