H1b Transfer extension without I-140 approval notice- Approaching 6 years limit

[ardentaj]

I have my I-140 approved with my current employer A however they haven't shared any details pertaining to that and now I need to move to employer B through h1b transfer but my total stay in US is about 4.5 years. I mentioned employer B attorney about my situation and they mentioned they can apply for h1b extension for 3 years even without I-140 copy and just by mentioning that since I-140 is employer's property we couldn't obtain it. So wanted to know whether this is even possible and has anyone successfully got extension like this ?