Can an indirect distinction on the basis of nationality or an impediment to the free movement of workers – requiring justification – be said to exist if the legislation of a Member State allows the tax-free reimbursement of extraterritorial expenses for incoming workers and a worker who, in the period prior to his employment in that Member State, lived outside that Member State at a distance of more than 150 kilometres from the border of that Member State may, without the provision of further proof, be granted tax-free reimbursement of expenses calculated on a flat-rate basis, even if that amount exceeds the extraterritorial expenses actually incurred, whereas, in the case of a worker who, during that period, lived within a shorter distance of that Member State, the extent of the tax-free reimbursement is limited to the demonstrable actual amount of the extraterritorial expenses?