I was in the exact situation as the original poster. My company used Notes with BES but only would put you on the BES if you were Director and above.

I did what the second poster suggested and setup a mail forwarding rule. It took about three weeks before one of the Notes admins disabled it and contacted me because it was against company policy to have a blanket rule that forwards internal emails to un-secure external addresses.

If your company is large enough to pay for the infrastructure needed to have Notes/Domino and a BES for Director+ level employees, I'm going to guess there's a 96% or greater chance your company has a similar policy.