between, from your statement, it seems like you mean connection fee should be borne by developer?

i think tnb won't involve themselves in arguing who should pay for the connection fee.
as long as they get the money... and yes, it's already been paid by the developer, and now claiming it back from buyers. 

it's a serviced apartment.
commercial, single phase = rm1280
(the developer's marketing team and sales agents have been telling the buyers that electrical would be on residential rate, but not sure why they are requesting for a commercial-rate deposit. by right should be around 700. this is another separate argument though.)

back to the issue of connection fee, in SPA generally has clearly stated the following:

"purchaser shall be liable for and shall pay, within 14 days bla bla bla, the deposits for the installation of water, electricity and gas meters and the Vendor shall bear all other costs, if any"

from my understanding, connection fee is not part of the deposits.