A temporary purpose does not create eligibility. The file still needs a qualifying relationship between the entities, the required period of continuous qualifying employment abroad within the relevant preceding period, and special knowledge of the employer's products, services, or advanced processes that the assigned work actually uses.
Check the qualifying year against the calendar
Prior time working in the United States can affect how the qualifying period abroad is counted, and people on repeated short deployments are exactly the ones this catches. Lay out the last several years as a simple timeline of where the person worked and for which entity, then have counsel review it. Doing this before the assignment is announced avoids a plan built on a period that does not count as expected.
Two boundaries belong beside that timeline. Where the person has spent time in the United States in certain classifications, that time can affect both how the qualifying year abroad is counted and how much of the five-year L-1B maximum remains available, so a history of repeated deployments deserves examination before anyone treats a further assignment as routine. Say as well what makes the knowledge specialized, because a finite assignment with clear deliverables can still rest on skills any experienced practitioner would hold.
Hypothetical example: a stage automation control specialist has completed three short U.S. projects in five years, and the useful first question is not what the next assignment involves but what those earlier periods did to the arithmetic, which is a question about dates and classifications rather than about the person's ability.