I don't think you can argue that Apple has a monopoly on smart-phone OSes, so it's not really an anti-trust issue like it was with MSFT. If you don't like it, get a different phone.
That was also only one part of the anti-trust case against Microsoft. They, at the time, had a very aggressive policy towards competitors and potential competitors. Going so far as, among other things, threatening to charge OEM PC manufacturers (IIRC, HP in particular) more for their Windows licenses (versus the discounted rate they got, eating into their margins or pushing their prices up) if they sold PCs with non-Windows OSes (such as BeOS, in particular).
They bought out competitors, shutdown development on products afterwards, things of that nature.
Apple's lock on their iDevices is certainly an issue, but they haven't hit half the checkboxes MS pulled off at the time of the anti-trust case.
Not to mention that that was MS imposing restrictions on devices sold by other manufacturers. This is them imposing restrictions on their own devices running their own software. I imagine there's a much higher bar for shenanigans before anything they do in that regard could get them in trouble.
