I agree with Rabini line of advise only for some points. Praysahnti there is no violation or objection in using your company logo and tag line till objection received by other person or company. I think you could have cross checked your logo and tag line availability before applying for registration in the form of official search report on the records of TMR. In that case you could have been got clear path. It is my considered view that using or making advertisement your company logo or tag line in public does not bar under Trade Marks Act, 1999,.
The opposite party should prove that your company logo and tag line is
Image of tag line
Is one of the same to their company logo and tag line.
As you said since you are making huge investment on the same, in case the opposite party has registration of the same they may sue infringement case against your company for damages of accounts in business and commercial line.
It is understood that after filing the application for registration of trademark, the person shall have use as TM only.
Better than the late consult the trademark attorney in this regard he will give inputs to gohead and to avoid unwanted litigation.
However I deny wordings of Rabin that “If the Respondent Co. has already registered it with logo or whatever, the TMR would not have accepted your application on the ground of deceptive simillarity, not novel and undistinctiveness, etc.” Dear sir TMR would accept the application even if it is close similar mark and there is no procedure to reject the application at filing stage. TMR would send Examination report to application to sought clarification from the applicant with quoting similar mark and fix for primary hearing the same, then only come to know to TMR of deceptive similarity marks. Rejecting at this stage are very rare cases, question of deceptive similar would be decided after heard the opposite party if opposed.
Dear praysahnhti go-head and do your project till object by other person.