No, it’s not possible to take lateral admission in a BA degree after completing a Civil Engineering diploma, in IDOL, YCMOU, or IGNOU. These two degrees are fundamentally different. You can get admission to BA after completing the course. But direct entry to second year isn’t possible. 

IGNOU offers direct admission to some of its degree programs. For example, if you have done your BCA from IGNOU, you can join their 2 year MCA program through lateral admission. So, IGNOU lateral entry has fixed eligibility criteria. You won’t be eligible for direct admission to second year in IGNOU MCA if you completed your BCA from any other university.