Employer-subsidised commuting costs on SNCB?

I believe I will be offered a job this week, and will be able to negotiate my salary a little. It's a large private company; the salary is ok for me, about 2,300, on a permanent contract (full-time position.)

I live within walking distance of the office now, in central Brussels. But I am 99% certain in December I will move to Wallonia, and commute by TEC bus (from my new place to local train station) and then with a Journey Railcard on the SNCB into Brussels Central.

My question is, are employers of a certain size obligated to help subsidise employees' transport costs on SNCB? (i.e. buying an annual or monthly railpass)?

I am wondering if, when negotiating a salary, I should mention that I likely will soon move and have increased commuting costs? (Obviously, if it's only a small amount of monthly salary I can negotiate anyway--I'd rather have the greater expense of my commuting costs subsidised instead of a slightly higher salary each month).

Or is OK to just negotiate the highest salary now, not mention the transport issue, knowing that the employee will have to, in the future, subsidise my commuting costs anyway?

Just in case my new living place in Wallonia falls through, I don't really want to mention it now. But at the same time, if I later explain that I have moved house and ask about subsidised transport, I don't want this to turn into 'you should have mentioned all this when you were first hired'!