If you think of it in terms of you're purchasing the tickets (but with Avios not cash), on expenses and the company just needs to reimburse you for the tickets. Then there isn't a case of selling the Avios as you don't have any cash changing hands for them, but the company will still be offering you recompense for having to travel on their behalf.

However you may come to a separate arrangement regarding travel with your company for the cost of flying on business (however you pay). You might have a structure whereby to various destinations (could be the bands BA use for example) they are going to pay you a fixed sum or buy you tickets to that value as part of an arrangement then there isn't a problem from an EC point of view. Now the taxman may find that against the rules however if they pay the taxes and fees on the redemptions and you declare the amount they give you as taxable income, i.e. you get reimbursed as extra pay and therefore pay tax on it then I can't see that as a problem. Having come across a stupid rule or two at HMRC I wouldn't put anything past them.