What is the type of this surface mount transistor?
Googling "SOT-23 transistor A4t" yields http://www.s-manuals.com/smd/a4 which suggests it might be a BAV70 dual diode, and http://www.s-manuals.com/pdf/datasheet/b/a/bav70_series_nxp.pdf datasheet, see section 4 on page 3 : Marking which says "BAV70 - A4" and "t: made in Malaysia".

I was thinking it may be diode logic to power a relay under two different conditions, but it could indeed be just flyback diodes. As such, I believe it's probably adequate ( 150mA continuous, 4A for 1 us! ) but if it failed short-circuit (as diodes do tend to do) it would prevent the relay operating.