I think I am correct in assuming that you are only talking of passing electrical services through the riser at certain points and not running them all the way up the riser?
The minimum space required between gas pipework and electrical services is 25mm.
(see Institution of Gas Engineers IGE/UP/2 Communication 1598 and BS 8313 : 1997 Code of Practice for Accomodation of Building Services in Ducts).
The Gas Safety Regulations 1972 and The Gas Safety (Installation of Use) Regulations 1998 require the gas installation to be of an acceptable standard and the riser to be adequately vented so as not to allow a build up of an explosive mixture.
It would appear that the answer is 'yes' but I would always suggest that you refer this to the design consultants assigned to the job. If they objected you could refer them to the above documentation.
Hope this helps.
