Symbology on standard terminal arrival (STAR) charts: T-ended vs arrow-ended lines? I was looking at the STARs at KPHX. The ARLIN FOUR arrival here has T-ended lines between the BLYTHE VOR and SCOLE, and between SCOLE and CALIE fixes. It also has arrow-ended lines between CALIE and HYDRR, and between HYDRR and PAYINT.

What does the difference in symbology mean?

At first I thought it indicated a different MEA, but then I looked at the DSERT TWO arrival here, and I see the T-ended lines between SHOCK and BUSTD, and between BUSTD and YOLOW, and the MEAs on both the neighboring segments is the same (9000).
According to the FAA Chart User's Guide, the arrows are transition routes and the 'T' is "Altitude change at other than Radio Aids." So your original assumption is correct.  

Regarding DSERT TWO ARRIVAL and BUSTD. You are correct that the altitude doesn't change at BUSTD when proceeding to YOLOW, but it does change (9000 to 8000) when proceeding to BAYTA. That is why there is a 'T' at BUSTD.