In most cases yes. If your exisitng brick work is in good condition and has been installed correctly it is possible to increase the height of your existing gate piers. Most gate installers will provide a free quotation to carry out the work and some will be able to provide all brickwork needed as part of the install.
This is definitely not something we would recommend. Electric gate installations should be carried out by professional engineers who are experienced and are registered CAME approved installers.