Here is a current-ish* list of all buses in Perth, sorted by depot and operator.

* (Page last updated: 14th September 2020)

While I have made every effort to ensure the accuracy of this list, it is mostly based on my own observations so I can’t guarantee it is 100% correct.

Path Transit

Bayswater:

Buses in depot: 58

1878-1899
2000-2003
2391-2399
2738-2746, 2748, 2749, 2751
3059, 3062, 3065, 3068, 3071, 3083, 3086, 3088, 3096-3098

Kalamunda:

Buses in depot: 45

2325-2362
3005, 3010, 3011, 3029-3032

Malaga:

Buses in depot: 121

104-108, 110-111
1399
1400-1413, 1462
1855-1877
2004-2012
2300-2324
2729, 2730, 2732-2737, 2759-2779
3001, 3002, 3035, 3038, 3041, 3044, 3047, 3050, 3053, 3077, 3080

Redcliffe:

Buses in depot: 56

2363-2390
2707, 2713, 2715-2726, 2731, 2747, 2750, 2752-2758
3016, 3017, 3027, 3028

Welshpool:

Buses in depot: 85

100-103
1363-1371, 1373-1387, 1389-1398
1414-1434
1591, 1592
1910-1917, 1919
2700-2706, 2708-2712, 2714, 2727, 2728

Swan Transit

Beckenham:

Buses in depot: 67

1666-1699
2400-2417, 2447-2454, 2456-2461
2568

Beenyup:

Buses in depot: 46

1355
1846-1850
2536-2552, 2557-2563
2886-2899
3200-3204

Canning Vale:

Buses in depot: 84

1656-1661, 1663-1665
2418-2425, 2463-2482, 2495-2499
2500-2513, 2568-2573, 2575, 2576
2817-2828
3034, 3052, 3055, 3058, 3061, 3064, 3067, 3076

Joondalup:

Buses in depot: 125

1220-1222, 1224-1230
1827
2148, 2152-2155, 2157, 2165-2199
2426, 2462
2574, 2586-2589
2600-2606, 2613, 2677, 2678, 2682, 2683, 2686-2698
2857, 2877-2885
2924-2927, 2933, 2939-2958, 2965, 2967, 2968
3033, 3039, 3042, 3057, 3078

Karrinyup:

Buses in depot: 103

2017-2095
2427-2446
3003, 3004, 3009, 3013

Midvale:

Buses in depot: 71

1466-1480
1662
2447, 2455, 2483-2494
2514-2535, 2553-2556, 2564-2568
2813-2816
3020-3022, 3082, 3085, 3087

Mount Claremont:

Buses in depot: 43

2848-2876
3014, 3019, 3023, 3037, 3040, 3043, 3046, 3049, 3070, 3079, 3099-3102

Shenton Park:

Buses in depot: 50

2577-2585, 2590-2599
2800-2812, 2829-2847

Wangara:

Buses in depot: 50

2124-2134, 2136, 2138, 2146, 2147, 2149-2151, 2158-2164
2244
2642-2643, 2660, 2679, 2680, 2684, 2685, 2699
2900-2905, 2909, 2910, 2917-2923

Southern River

Buses in depot: 72

1435-1439
1594-1596, 1599
1600-1609, 1610-1655
2013-2016, 2096, 2097
3007, 3026

Transdev

Claisebrook:

Buses in depot: 39

2139-2145
2610, 2617-2635, 2665-2676

Fremantle:

Buses in depot: 193

112-117
1234-1236, 1238-1251, 1253-1256, 1258-1268, 1270-1297, 1299
1900-1909, 1920-1941, 1979-1999
2200, 2273, 2274, 2277-2279, 2282-2292, 2297-2299
2607, 2608, 2647-2658, 2681
2912-2916, 2932, 2933-2938, 2959-2964, 2966, 2970, 2971
3000, 3036, 3045, 3048, 3051, 3054, 3060, 3063, 3066, 3069, 3072-3075, 3081, 3084, 3094, 3095

Mandurah:

Buses in depot: 77

1212-1219
2135, 2137, 2156
2216-2243, 2262-2269, 2271, 2272
2609, 2611, 2612, 2614-2616, 2636-2641, 2659, 2661-2664
2906-2908, 2911
3006, 3008, 3012, 3015, 3018. 3024, 3025

Rockingham: