Send this information to your employer:
http://www.cic.gc.ca/english/resources/tools/temp/work/permit/implied.asp
As long as you have applied for your new work permit BEFORE your old one expires and you DO NOT leave Canada while you are on implied status, you are definitely allowed to continue working for your current employer. Some employers might not be familiar with this rule so you have to be very clear about communicating this to them. You can also show them proof that you have applied for the new permit.