In order to be qualified for EB2 category at the 140 stage, it is required that the job requires at least a MS+0 or in lieu of MS, BS+5 yrs of "progressive" experience should be acceptable. See link below:
EB2 equivalency memo...
http://www.immigrationlinks.com/news/news215.htm
I am not sure if SWA will make a big issue out of the mere absence of the word "senior" in the job title. They look at the job description / responsibilities too. If the job desc says that you will be providing guidance to junior engineers or will be in involved in quality control of other Engineers' work or you will be interfacing with clients to coordinate their needs, then it may sound like a senior engineer position (team leader) based on which they may let you have MS+0 under item 14. Else, SWA may say that the normal requiremnet for "Civil Engineer" (without senior title or supervising responsibilities) is a BS+2 yrs of exp and may then challege MS+0 under item 14.
I was exactly in the same position as you (I had MS+0 yrs exp when I joined my sponsoring employer). However, my company gave me the senior title after 1 yr of employment with them. So my lawyer used the "Sr. Title" in the LC since it was applied after I got the Sr title.
Also, there is another question on ETA form 750A which asks the employer to fill the number of people the alien will be supervising...What did your lawyer enter for that question? My lawyer entered 1 to 3 persons and this makes it a senior level position (something like a team leader and not a manager).
If your company is not very fussy about signing the ETA 750A form and mentioning the Sr. title on the form and if they can state that you will supervise a few persons, then it may sound more convincing for a EB2 case. Also, note that LC is applied by employers for a
"future" permanent employment opportunity offered to the alien.
It will therefore not matter whether you currently have a "senior" title or not. If an LC with senior title gets approved, and if one uses that LC to get the actual greencard, then the employer MUST give the alien the "senior" title and the specified salary on LC from the day of 485 approval.