Controlled Group Status Changes

[Below Ground]

401(k) Plan uses the calendar year, and is notorious for providing data late. We just finally recieved 2012 data (after 4 written requests and numerous calls). In data submitted we find that ownership changed during the year so at year end, the three firms previously covered as a single employer are no longer a controlled group. Problem is when does this change apply to the Plan, and when does the Plan become a multiple employer plan. If we apply "multiple employer status" for 2012, one group under the Plan will fail ADP Testing and be considered Top Heavy. If status is applied in 2013, same problems for that year. During both years a key employee does contribute deferrals under the group that fails ADP and is Top Heavy, so where no employer contribution was used, a Top Heavy Minimum is required. Hoping there is a transition period under regs for this situation. Of course there has been no documentation on this topic processed. Any thoughts or insights? Thanks!

[Below Ground]