If Democrats use reconciliation to pass a health care bill and even one Senate Democrat actually supports the public option, or one Senate Republican thinks it makes political sense to force a vote on the matter, there will likely be a vote on a standalone amendment to add a public option. One of the important aspects of reconciliation is that any amendment offered normally gets an up-or-down vote provided it meets the rules.
According to the rules of budget reconciliation, debate is limited to only 20 hours in the Senate. At the end of debate, pending amendments which are germane and don't violate the Byrd rule normally get up-or-down vote. Neither reconciliation measure nor amendments to a reconciliation measure can be filibustered.
A rapid process of voting on the pending amendments to the reconciliation measure is called a "vote-arama." From the Congressional Research Service (PDF):
When the 20-hour debate limit has been reached, Senators may continue to consider amendments and motions to recommit with instructions (and to take other actions as well), but they may not debate them unless unanimous consent is granted. The circumstance under which debate time on a reconciliation measure (or budget resolution) has expired but amendments and motions continue to be considered has come to be known as "vote-arama." As a general matter, accelerated voting procedures sometimes are put into effect under a vote-arama scenario, allowing two minutes of debate per amendment for explanation and a 10-minute limit per vote.
A public option and/or some form of Medicare/Medicaid/Tricare buy-in should be able to easily be designed to be germane and not violate the Byrd rule. If cost savings and the fact that the program would technically be on the budget are not sufficient to satisfy the Byrd rule, other steps can be taken; for example the "reference plan" which is used to instrumental for calculating the amount of tax credits on the exchange could be replace with cost of premiums for the public option.
If any one senator offers a public option amendment to the reconciliation bill, or better yet, several amendments of different variations of public health insurance alternatives, it should likely get an up-or-down vote during the vote-arama.
The biggest concern is that a public option amendment would be swept up in an action to stop a Republican filibuster by amendments. Awhile back Republicans were threatening to use the "vote-arama" to create a filibuster by amendments by offering thousands of amendments to stop the final passage of the reconciliation measure. If Republicans attempt this, David Waldman outlined how Harry Reid and Joe Biden could put a stop to it. In theory the public option amendments could be swept up in the effort to clear hundreds of Republican amendments.
Harry Reid and Joe Biden might use clearing on any planned Republican filibuster-by-amendments to stop the public option from getting a vote, or some other parliamentary trick to do the same. Of course this would require Reid and Biden to actively take steps to deny the American a vote on one of the most popular provisions related to health care, which they both claim to support.
If (and that is a big if) Democrats move forward with health care reform using reconciliation, it is likely that there will eventual be an up-or-down vote on the public option. All it takes is one senator to offer a properly designed amendment - perhaps one of the 30 Senate Democrats who are on record saying they support an up-or-down vote on the public option. Maybe the American people will finally get to see who stands with the American people and which senators are working to protect the profits of the private insurance companies.